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Vulpes vulpes

Content Updated: 28th April 2014


Evolution and Early Distribution
  North American Red foxes
  British Red foxes
Appearance and Colour
  Samson foxes
Ageing and Longevity
Mortality and Disability
Parasites and Diseases
Dens/Earths and Resting Sites
Territoriality and Home Range
Food and Feeding
  Types of prey consumed
  Prey switching
  The influence of age and sex on diet
  How much food?
  Hunting strategies and behaviour
  Killing to ‘excess’ and the storage of left-overs
Breeding Biology
  Reproductive development
  The number of breeding vixens
  Mating and monogamy
  Gestation, birth and litter size
  Growth and development of the cubs
Behaviour and Social Structure
  Live and let live: the evolution of group-living
  With a little help from my friends: ‘helpers’ in fox society
  Keeping order and knowing your place: the social hierarchy
  All in the name of fun: fox body language
  Nightly interactions
  Communication: something to shout about
Interaction with Humans
  The fox in literature and film
  The emblematic fox
  Foxes held in high esteem: gods, devils and worship
  The fox as a resource: fur, meat and sport
  The verminous fox: foxes as pests
  Man’s best friend? Fox domestication
  Living with the wild: interacting with wild foxes
Interaction with other Species
  Small and Medium-sized Mammals
  Arctic Foxes and other Carnivores
  Native Animals in Australia
  Plants and Invertebrates
Questions and Answers

Red Fox Stalking

Evolution and Early Distribution: Dogs and cats are Carnivorans, that is, they’re members of the taxonomic order Carnivora (note this is different to simply being a carnivore, or meat-eater, which is not a taxonomic grouping), which is one of 29 orders within the class Mammalia. The evolution of carnivorans appears to have been a gradual process that happened in both North America and Eurasia, making it difficult to infer when it all started. Nonetheless, taxonomists (those who study how species are related to each other) currently think that the carnivorans evolved from animals called miacids, which were small tree-living mammals that looked similar to modern-day civets. At some point -- by current thinking, around 42 million years ago (mya), during the mid-Eocene -- it appears that the carnivorans split into the two groups, or suborders, that we recognise as cat-like (Feliformia) and dog-like (Caniformia). If, at this point, you’re wondering where mammals like mustelids, seals, bears, etc. fit in: they’re all dog-like carnivorans.

The evolutionary history of the dog family is still not completely resolved (and may never be, as new fossil finds and molecular techniques offer new insights), but the following is a generally accepted hypothesis. Readers interested in a more detailed appraisal of dog evolution are directed to Xiaoming Wang and Richard Tedford’s authoritative account in their 2008 book Dogs: Their Fossil Relatives and Evolutionary History and I recommend the reader visits WikiPedia and The Searching Wolf. Briefly, the creature that taxonomists currently think gave rise to modern-day dogs was a medium-sized (about the size of a coyote) grassland predator of North America called Prohesperocyon wilsoni that appeared during the late Eocene, some 36 mya. The caniforms subsequently diverged into three lineages (which we call subfamilies): the Hesperocyoninae (‘western dogs’); the Borophaginae (‘bone-crushing dogs’); and the only one still around, the Caninae, which includes the dogs, wolves, foxes, etc. and is thought to stem from the now extinct small fox-like Leptocyon, which lived in North America. During the late Miocene, around 10 mya, something important happened: the third, and for our purposes most important, canid radiation began. This radiation was probably in response to a vacant niche opening up as the borophagines started to die-out, and not only marked the birth of all the dog species we know today but also heralded the appearance of three modern-day genera in the south-western USA: Canis (dogs, wolves, dingoes, etc.); Urocyon (Gray foxes); and Vulpes (true foxes). In essence, it was around 10 mya that the fox lineage split from the wolf-dog lineage. A couple of million years later the dogs started arriving in Eurasia, and the Pliocene (4-5 mya) saw the dogs spread into Africa and South America. Around six mya, the first wolf-like dog arrived in western Europe.

According to Wang and Tedford, the first true foxes appeared in North America late in the Miocene (around 9 mya) and were represented by a small Californian species known as Vulpes kernensis, and a larger species (V. stenognathus) that was found throughout the continent. Foxes spread out from North America, presumably via the Bering land bridge, and colonised Europe. The oldest Old World fox specimen so far identified is V. riffautae, which was found in the Central African country of Chad and dates to the late Miocene (some 7 mya). Recent work by Louis de Bonis and colleagues at the Université de Poitiers in France has suggested that the foxes and other canids first spread throughout Africa, before invading Europe via a trans-Mediterranean route towards the end of the Miocene. There is then something of a hiatus in the vulpine fossil record until the early Pliocene (about 4 mya), with foxes from China and Turkey among the earliest Eurasian specimens. The origins of our modern-day Red fox (V. vulpes) is equivocal, although most authors agree that it is descended from the Eurasian red fox Vulpes alopecoides, which lived in southern Europe at the end of the Pliocene, around 2.6 mya – this species was first discovered in deposits from Italy in the late 1800s, but remains were subsequently found in France, Spain and Greece.

In their 1982 comparison of Red and Arctic (V. lagopus) fox ecology, Pall Hersteinsson and David Macdonald note that both species are descendents of V. alopecoides and that the two species diverged during the Pleistocene. Indeed, the earliest fossil evidence for V. vulpes comes from the Old World and dates to the early Pleistocene (between 1.8 and 1 mya) of Hungary and, in her 2008 study of Red fox dentition, Polish Academy of Sciences mammalogist Elwira Szuma suggested that the current V. vulpes line evolved either in Asia Minor or North Africa around this time. As fox populations rose in Eurasia, those in North America appear to have dwindled. Previously it was believed that the first modern Red foxes (i.e. V. vulpes) to appear on the continent migrated (again, presumably across the Bering land bridge) from Europe at the end of the Pleistocene (around 1 mya) and, from here, Red and Arctic foxes colonised much of North America. Recent genetic work by Keith Aubry and his colleagues at the Pacific Northwest Research Station in Washington, however, has revealed new information on the spread of the Red fox in North America. Aubry’s data suggest that this species first reached North America during the Illinoian glaciation that lasted from roughly 300,000 to 130,000 years ago; during the next 30,000 years (the Sangamon interglacial period) the foxes spread south from Alaska, across what is now the contiguous USA. The large ice sheet that covered most of Canada and the northern fringes of the USA from around 100,000 to 10,000 years ago (during the Wisconsin glaciation) kept the Red foxes in Alaska (the population of which was added to by a second wave of colonisation from Eurasia) separate from those in the southern USA. So, the result was two isolated populations (or clades): one in Alaska (Holarctic clade) and one in the south (Nearctic clade). When the ice melted the Holarctic clade spread south and east, while the Nearctic clade spread north, the two meeting in central Canada. Aubry’s data reveal more than just the distribution of foxes in pre-history, it also elucidates the relatedness of the animals currently inhabiting North America (see: Taxonomy).

Whenever and wherever this species first appeared, fossil evidence suggests that the modern Red fox has been in North Africa for the last 700,000 years and Europe for at least the last 400,000 years. In Britain, remains of the Red fox have been found in Wolstonian Glacial sediments from Warwickshire, suggesting that they were around between 330,000 and 135,000 years ago. Following the retreat of ice from the last ice age (the Late Glacial) some 15,000 years ago, many of the larger mammal species began to re-appear and extend their range northwards. According to Derek Yalden’s fascinating book, The History of British Mammals, post-glacial remains of the Red fox have been found at several sites around Britain and suggest that this species re-appeared ‘naturally’ (i.e. without any obvious assistance from humans) around 10,000 years ago. Indeed, other fossil data imply that the ice forced foxes into the warmer southern regions of Europe (e.g. Iberia, Italy, southern France, etc.) for only a (geologically) brief period, after which they quickly returned to central Europe and Britain; at the time, the UK was connected to the European continent. The flooding of the Doggerland ‘bridge’ around 6,500 years ago isolated Britain’s foxes from those in Europe, putting an end to any natural mixing of the populations. (Back to Menu)

Red Fox portraitTaxonomy: Many texts on fox natural history cannot help but draw comparisons between the fox and the cat and, if you spend any time watching them, you’re certainly struck by how similarly they behave: both have the same delicate, tripping gait; both stalk and pounce in much the same way; both sit and sleep with tails curled around their bodies; both twitch tail tips to allow young to practice hunting; both will use a paw to scoop unwary fish out of a garden pond. Anatomically, however, foxes have the large ears, the long pointed muzzle, the 42 teeth and the non-retractable claws (five on forefeet and four on hind) that we typically associate with dogs, although they do share the vertically-slit pupils commonly associated with cats (larger canids, such as wolves and domestic dogs, have round pupils). Despite the resemblance, foxes are dogs not cats; the feline similarities are a result of convergent evolution, where two species look similar because they occupy a similar ecological niche and/or habitat. (Sharks and dolphins provide a good example of convergent evolution. They look very similar but aren’t related. They have evolved the same basic body shape because it works very well in aquatic habitats).

Foxes have been a well-known part of our countryside for many centuries (see: Interaction with Humans), but Swedish scientist and father of modern-day taxonomy, Carl von Linne (often known simply by his pre-ennoblement surname, Linnaeus), was the first to formally describe and classify the Red fox in the 10th edition of his Systema Naturæ, published in 1758. Based on a specimen from Uppsala, the university town of south-east Sweden in which he studied, Linnaeus gave the animal the Latin name Canis vulpes (meaning literally ‘dog fox’), recognising its place within the dog family. The principal idea behind classifying animals is to illustrate their relatedness, so closely related species are grouped together (in the same genus, for example), while more distantly related ones sit further away. As was the case with much early taxonomy, as more species were described and interrelationships became better understood the initial groupings proposed by Linnaeus for the dogs soon became too restrictive to adequately reflect their diversity; this led to the creation of new genera within the dog family (Canidae). One such genus is the one we now use for most of the modern-day foxes: Vulpes.

Until very recently, the creation of the genus Vulpes was credited to German zoologist Just Leopold Frisch. In 1775, Frisch published his thesis on the ‘systematic table of four-footed animals’ in which he curiously described the ‘common fox’ as both Vulpes vulgaris (vulgaris meaning ‘common’ in Latin) and Vulpes crucifer (confusingly, both names referred to the same animal). Following Frisch’s lead, Vulpes was used by many subsequent authors when referring to the Red fox. Indeed, since about 1900 there has been almost universal reference to Vulpes vulpes, rather than Canis vulpes. Unfortunately for Frisch, he didn’t follow the taxonomic rules and so, in 1954, the ruling body on such matters (the International Commission on Zoological Nomenclature, or ICZN for short) rejected his work, which meant that it couldn’t be used by taxonomists.

Not everyone was happy with the ICZN’s stance and considered that it was confusing. Fortunately, the ICZN revoked their initial ruling in August 1979, almost five years after Juliet Clutton-Brock and Gorbon Corbet (both mammalogists at London’s Natural History Museum) submitted a proposal to them arguing that the name Vulpes was recognised throughout the world (and had been since the start of the twentieth century) and that it was more important to be consistent in our naming than it was to strictly follow the rulebook. In other words, for the last 75 years people have been using Vulpes to refer to foxes and it’ll confuse the heck out of them if we now say they can’t use that and need to use Canis instead! The ICZN didn’t entirely agree with this argument, but decided that Vulpes was such a well-known name that an exception was justified. So, most (although, as we shall see, not all) taxonomists returned to using “Vulpes Frisch, 1775” as the genus for most members of the fox group. In 2008, however, Francisco Welter-Schultes and Rebecca Klug at the Zoologisches Institut der Universität in Germany discovered an almost unknown early work on animal and plant taxonomy by French naturalist François Alexandre Pierre de Garsault, which he published in 1764. In this volume, Garsault used the genus Vulpes without a species, but accompanied it with a drawing of a Red fox. In taxonomic circles there is a rule of preference saying that the earliest valid name or reference has priority and, as Garsault used Vulpes in the same sense as, but 11 years earlier than, Frisch, he gets the nomenclatural credit. In other words, Garsault is credited as the first person to use (the ‘inventor of’, if you like) the genus Vulpes for foxes and authors using “Vulpes Frisch, 1775” need to amend the reference to say “Vulpes Garsault, 1764” instead.

The precise point at which the Red fox was first placed in the Vulpes genus seems to have been lost in antiquity, but many early nineteenth century writers used Vulpes as a subgenus within Canis -- so the Red fox was referred to as Canis Vulpes vulpes -- and this continued until relatively recently. By the 1820s, British zoologist John E. Gray was using Vulpes as a genus and, in their 1832 Symbolae Physicae Mammalia, German naturalists Wilhelm F. Hemprich and Christian G. Ehrenberg recognised that the foxes could be grouped apart from the wolves and proposed the Vulpini (a taxonomic grouping called a tribe, that sits between the family and genus level) for them. In 1846, writing in the first volume of their Viviparous Quadrupeds of North America, John J. Audborn and the Rev. John Bachman grudgingly elevated Vulpes from subgeneric to generic level, spurred on by the sheer number of species already held within Canis:

The characters of this genus differ so slightly from those of the genus CANIS, that we were induced to pause before removing it from the subgenus in which it had so long remained. As a general rule, we are obliged to admit that a large fox is a wolf, and a small wolf may be termed a fox. So inconveniently large, however, is the list of species in the old genus CANIS, that it is, we think, advisable to separate into distinct groups, such species as possess any characters different from the true Wolves.

The characters Audborn and Bachman were referring to, that separate the foxes from wolves, include the pointed muzzle, vertically-slit pupils, only slightly curved incisor teeth, slender form, relatively shorter legs and long, thick, bushy tail. Various taxonomic arrangements were subsequently proposed, some following Audborn and Bachman’s decision and others opting to either ignore Vulpes, or relegate it to subgeneric status. It would be 34 years, however, before a significant attempt at arranging the members of the Canidae was published.

Corsac Fox     Fennec Fox

The Vulpini (fox) tribe is a diverse mixture of some 37 species adapted to live in a range of habitats, from parched deserts to forzen ice floes. One of the five genera within this tribe, Vulpes, contains the 'true foxes' - 12 species that include grassland specialists like the Corsac fox (Vulpes corsac - above left), desert specialists like the Fennec fox (Vulpes zerda - above right), artic surviors such as the Artic fox (Vulpes lagopus) and, of course, the generalist Red fox (Vulpes vulpes).

Driven by his disillusion with previous attempts to classify the members of the dog family, the great London-born physiologist, and evangelical evolutionist, Thomas Huxley published his detailed study on the classification of the Canidae in the Proceedings of the Zoological Society of London during August 1880. In this magnum opus, Huxley divided the canids into two groups based on various cranial and dental characteristics: the Alopecoids (true foxes) and the Thooids (hunting dogs, wolves, and South American foxes that are currently assigned to the Lycalopex genus). Huxley, however, retained the Red fox as Canis vulpes. Nonetheless, the late 1880s represent the point at which canid classification stabilised; at this point we had most of the species that we currently consider to be members of the Canidae.

Following Huxley’s scheme, Canis and Vulpes were variously used when referring to the Red fox and some, Clarence L. Herrick in his 1892 Mammals of Minnesota for example, were still using Frisch’s specific name vulgaris (i.e. Vulpes vulgaris), rather than vulpes. By 1912, however, Gerrit Miller had adopted Vulpes vulpes in his ‘Catalogue of the Mammals of Western Europe’ and, in 1945, Simroe Foundation mammalogist George G. Simpson published his classification of mammals in which he split the dogs into three subfamilies, with all the living species placed into the Caninae. Simpson recognised Vulpes as a genus within the Caninae, but noted how:

…the recent canines are quite uniform in structure, and it would be justified from many points of view to unite them all in a single genus.

We then had Clutton-Brock and Corbet’s argument to the ICZN and the eventual ruling in 1979. Just before this ruling (in April 1978), however, American Museum of Natural History curator Richard Van Gelder agreed with Simpson’s 1945 concerns and relegated Vulpes to a subgenus within Canis once more. Nonetheless, the ICZN has the final say on these matters and, under their Opinion 1129 (1979), it was ruled that Vulpes vulpes is the valid name for the European Red fox. In order for a taxonomic group to be considered valid it needs to contain all the descendents of a common ancestor (we call this a monophyletic group); if it doesn’t (i.e. it’s missing some, or has ‘extras’) it’s considered invalid, or paraphyletic. Overall, it seems that the ICZN made the right decision and recent molecular studies have shown that Canis is paraphyletic. There has been much work recently using different genetic markers to assess relatedness among the Canidae and each has proposed slightly different arrangements. To avoid dragging this section on unnecessarily, I won’t go into the details of them here.

The current situation is that the Canidae contains 36 species that can be divided into two broad groups (Tribes): the Vulpini, which contains the fox-like canids; and the Canini, which contains the dog/wolf-like canids. It is the Vulpini that interest us here and this tribe contains three genera: Otocyon (Bat-eared fox); Nyctereutes (Raccoon dog); and Vulpes (true foxes). The six species of South American fox (Lycalopex) and the Crab-eating fox (Cerdocyon thous) are grouped within the Canini. It seems that the red fox group is only monophyletic if it includes two species that were previously split out: the Arctic fox (Alopex lagopus) and the Fennec fox (Fennecus zerda). Thus, it is now widely accepted that these species are Vulpes lagopus and Vulpes zerda respectively, and this brings the number of species currently held within the Vulpes genus to 12. Some authors have suggested that Vulpes is paraphyletic unless it contains Nyctereutes, but a study published in the journal Molecular Biology Reports in 2011 found no support for this, placing the Raccoon dog and the true foxes as sister groups (i.e. more closely related to each other than to any other group).

The Red fox shows what we call biological plasticity – in other words, they’re capable of adapting their form to handle different environments. The result is that Red foxes living in different parts of the world can look significantly different to each other. Consequently, there are currently 48 proposed subspecies of Vulpes vulpes, based on differences in size, skeleton, teeth, colour, etc. No doubt some of these populations have been separated for long enough to make some of the subspecies valid, but it is very difficult to establish which they are and it seems very unlikely that all 48 are valid. A recent (2007) study led by Takashi Inoue at Hokkaido University suggested that there were two subspecies of Red fox living in Northern Japan; one being the common Eurasian fox and the other being unique to Hokkaido. Anthony Mitchell-Jones and his co-workers were sceptical about the number of proposed European subspecies and, in their 2002 Atlas of European Mammals, considered a maximum of five -- more likely four -- to have any true validity. Using a small sample of foxes collected from across the Northern Hemisphere, Paolo Cavallini found that he could divide them into three groups based on size. In his 1995 paper to the journal Annales Zoologici Fennici, Cavallini explained:

Red foxes from North America are comparatively light, rather long for their mass and with a high sexual dimorphism. British foxes are heavy but relatively short, whereas European foxes are closer to the general average among populations…

Cavallini goes on to note that British foxes were more similar to European animals than to those in North America; his sample was relatively small (20 populations), but the data certainly suggest a separation is warranted and further, larger scale, studies should prove rewarding. Cavallini was not the only person to see such a difference between foxes on different continents and, although most biologists lump British and European foxes together, some recognise a distinction between Eurasian and North American foxes; the two are sometimes considered different subspecies (even different species by some).

North American Red foxes
North American Red fox
Early naturalists described several species of Red fox from North America (photo, right) based on differences in size, colour, skull dimensions and geographical range. By the end of the eighteenth century, however, most of these had been synonymised with (considered to be ‘types’ of) the widespread American Red fox, Vulpes fulva (fulvus is Latin for ‘reddish-yellow’ or ‘tawny’). A study, during the late 1950s, of the pelts and skulls of foxes collected in the US and compared to those from Eurasia found a general ‘cline’ in the foxes, concluding that the American fox isn’t a distinct species; instead it is a race/subspecies of the Eurasian fox. Some relatively recent genetic work suggested that there are two major ‘groupings’ (or clades) of foxes in North America: foxes in Alaska and western Canada were grouped together with those from Eurasia to form a Holarctic clade, while those in some southern and eastern states formed a second, genetically-distinct, Nearctic clade that is made up of animals unique to North America. At some point during the Wisconsin glaciation, the suggestion is that the Nearctic clade split into two subclades; one in the east and one in the west.  When the ice melted, around 10,000 years ago, foxes in the east (the eastern subclade) followed the boreal forests north and colonised eastern and central Canada. Foxes in the west (Mountain subclade), however, colonised the alpine meadows and subalpine parklands of high mountains. Within the mountain subclade, there are four subspecies of apparently indigenous animals: three subspecies of ‘mountain fox’ that are restricted to high-elevation montane and alpine habitats of the Cascades, the Sierra Nevadas, and the central Rocky Mountains; and a subspecies unique to the Sarcramento Valley. It seems that the mountain foxes are better adapted to the cold, harsh conditions at high altitude and do not mix with foxes from low elevations. In Yellowstone, for example, it appears that foxes living above 2,100m (6,900ft) are genetically different to (and don’t mix with) those below this altitude.

Early European settlers released Red foxes -- transported from Britain, France and Scandinavia -- along the eastern seaboard (i.e. the eastern coast of the USA, from Maine in the north to Florida in the south) for hunting purposes as early as the mid-1700s. It had previous been considered that these animals spread quickly, either displacing or inter-breeding with the indigenous lowland populations, which appear to have been very thin on the ground at the time. Releases continued for many years afterwards and the population was added to by escapes and releases from fur farms, most of which were also foxes of European origin. Many authours had been of the opinion that all this inter-breeding between the indigenous stock and released animals had invariably served to ‘dilute’ differences between the native and non-native populations in most areas, and some have suggested that the Red fox common throughout lowland North America today is actually a hybrid of many different subspecies from across the species’ range.  The conclusion, therefore, was that there is little justification for considering the lowland American Red fox distinct from that found in Eurasia, although it was acknowledged that -- as discussed above -- some native populations still survive and do not appear to mix with non-native populations; such native animals were typically considered subspecies at best, although the potential is there for their evolution to distinct species. More recently, however, the pciture in North America has changed a little. In a paper to the Journal of Mammalogy in February of this year (2012) Kansas State University biologist Mark Statham and colleagues presented their data on the origin of the recently established fox populations in North America. Statham and his co-workers compared the mtDNA profiles of foxes from six recently established American populations to that of animals from Eurasia, Canada and fur farms. Intriguingly, the researchers found no Eurasian haplotypes among the North American Red foxes (i.e. these US foxes didn't share any genes or gene combinations with the foxes in Europe or Asia, which one would expect if the American foxes were descended from those in Eurasia). The findings of this study warrant further investigation and sampling (particularly of foxes in the east), but the data certainly suggest that, despite the number of foxes imported to (and moved around) the North American continent during colonial times, non-native (introduced) lineages have only survived in areas where native stock were absent. The data reveal a deep phylogentic split, which suggests an ancient division within North American foxes. In other words the biologists found that North America is composed of two very distinct lineages of Red fox; one (i.e. those in Alaska and Western Canada) split from those in Eurasia quite recently ( circa 50,000 BP), while the other (i.e. those in the Western mountains of the US, Sacramento Valley, California, and Eastern Canada/US) is much older, originating during the Illinoisan glaciation (circa 300-500,000 BP). While these data don't suggest that all North American Red foxes are a separate species from those in Eurasia, they do raise the question of whether there are two distinct species within North America. (For more information, please see the Q/A)

British Red foxBritish Red foxes
The subspecies Vulpes vulpes crucigera was described from Germany by naturalist Johann Bechstein in 1789. This subspecies, which was noticeably smaller than the one Linnaeus described from Sweden 31 years earlier (the ‘type’ specimen), had noticeably different teeth -- they were smaller, with widely spaced premolars that had obsolete or absent secondary cusps -- and a brighter yellowy-red coat than the type specimen. In his 1912 Catalogue of the Mammals of Western Europe, former United States National Museum curator of mammals Gerrit Miller Jr agreed with Bechstein that this was a valid subspecies -- one of three found in Europe -- and gave its range as central and southern Europe, from Ireland east to Greece. There has been much debate about whether it is really possible to lump foxes from particular areas together and whether tooth size and spacing is actually too variable among foxes to offer evidence of taxonomic separation. Releases of foxes imported from Europe in Britain during the 17th Century and the interbreeding that almost certainly occurred between them and indigenous stock further weakens the argument for separation. Indeed, it is rare to find post-1980 authors who consider crucigera to be a valid subspecies. There are some genetic data from foxes in the Mediterranean that suggest distinct groups do exist and that there may be a case for assigning some subspecies, but the data simply don’t exist for a sufficiently large geographical area to be certain whether similar groupings can be applied to other Eurasian populations. Indeed, a paper published in the journal BMC Evolutionary Biology during 2011 looked at DNA samples from modern and ancient (fossil) Red foxes from across Britain and Europe and found no clustering of any sort and strikingly little apparent change in population size over time. The authors concluded that:

It is probable that the high dispersal ability and adaptability of the red fox has contributed to the lack of observable differentiation, which appears to have remained consistent over tens of thousands of years.”

In other words, rather than foxes being split into small groups in ice-free regions (so-called ‘refugia’) at the last glacial maxima (which could, through inbreeding, allow the build up of unique genetic traits that make each population different from another), the population was pushed back as one large interbreeding group. Consequently, the majority of biologists now consider that Vulpes vulpes is just a highly variable species that ranges throughout Europe and Asia and do not attempt to categorize it further. (For more information, please see the associated Q/A)

Finally, there has been some suggestion that urban and rural foxes may be separate subspecies. To date, I know of no evidence in support of this. Indeed, radio-tracking studies by several teams have shown that urban and rural foxes can and do mix. The data do, however, paint a mixed picture, with some animals dispersing out of one town, crossing several kilometres of potentially suitable rural habitat, to settle in a neighbouring town; others have dispersed from rural areas into towns and cities, while some have done the opposite. The Bristol University team are quick to point out that there can even be very short-term visits; rural individuals have been tracked entering neighbouring urban areas at night to hunt. In a 2003 paper to the journal Molecular Ecology, a team of scientists from the Zoological Society of London and University of Zurich published their data on the foxes living in the Swiss city of Zurich. The researchers found that, although urban foxes appeared to breed most often with other urban animals (unsurprising, given their social system), urban and rural animals also interbreed. Indeed, the authors wrote:

"Currently observed levels of migration between urban and rural populations will probably erode genetic differentiation [between urban and rural populations] over time."

Consequently, pending genetic data to the contrary, the Palaearctic and North American Red fox is classified as follows:

Kingdom: Animalia (Animals)
Phylum: Chordata (Possess a basic 'backbone')
Class: Mammalia (Mammals)
Order: Carnivora (Possess carnassial teeth)
Family: Canidae (Dogs)*
Tribe: Vulpini (Fox-like canids)
Genus: Vulpes (from Latin meaning 'fox')
Species: vulpes

* Note: Some authors place foxes within their own subfamily: the Vulpinae. Here, however, I am following Ingi Agnarsson, Matjaz Kuntner and Laura May-Collado’s 2010 phylogeny of the Carnivora.

For more information on how species are classified see: Taxonomy. (Back to Menu)

Red fox curled upSize: The Red fox is the largest member of the Vulpes genus and shows enormous variation in size across its range; they’re also deceptively difficult to size at distance, often appearing larger than they really are – most foxes are about the same size as an adult domestic cat. Globally, most individuals have a head and body length (HBL) in the range of 45cm to 90cm (1.5 – 3ft); add an extra 30cm to 50cm for the brush (tail) and foxes can reach a total length of about 150cm (just under 5ft). In the UK, adult male foxes typically range in HBL between 67cm and 72cm (26 - 28in.), while females fall between 62cm and 68cm (2ft – 2ft 4in.). The tail makes up just over one-third of the total body length and the longest record for a brush I have come across is 55.5cm (almost 2ft!). In his 1950 book, Wild Animals in Britain, Oliver Pike described one “magnificent creature” that measured 64 inches (163cm) from nose-to-tail. By looking at skull and tooth size measurements, Polish zoologist Elwira Szuma found that the largest Nearctic foxes were those from Alaska’s Kodiak Island and the Kenai Peninsula, while the smallest lived in California and Georgia; in the Palearctic, the largest foxes come from the Far East while the smallest are from the southern borders of the Eurasian range. Within Europe, Szuma found that Scandinavian foxes are the largest, followed by those in Britain.




There are many stories of large foxes having been spotted; the most recent one I have come across was an interesting account of a fox the size of a “large roe deer” that was reported near Tilford in Surrey on 30th April 2011. Unfortunately, there was no photographic or video evidence of the animal and, although the witness watched the animal for several minutes and was convinced it was “absolutely a fox”, such reports remain unconfirmed. Invariably, most reports of very large foxes are cases of mistaken identity – several dog breeds, including long-haired Alsatians and Red Huskies, can look very fox-like under some conditions. Even dogs that don't have any particularly 'foxy' colour to them can, under certain circumstances, appear very fox-like, as the below photo -- sent in by Wildlife Online reader Lynn Harrison -- of a husky having been lying in the ashes of a bonfire shows. From time-to-time, however, large foxes are recovered.

Fox-coloured husky
Even dogs that don't normally appear particularly fox-like in the colouration can sometimes take on a rather 'foxy' appearance. This husky ended up with a foxy tinge to its coat after playing in the ashes of a bonfire. A quick glimpse of the dog in its above condition could easily be mistaken for a 'giant fox'.


Red fox in grass

Following the capture of the ‘Kent cat killer’, concerns were raised in the media that access to a superabundance of food in our towns and cities was breeding bigger foxes, and various unverified statements about how urban foxes were getting bigger appeared in the press. Such claims may have some grounding but, to the best of my knowledge, we currently have no documentary evidence to support the oft-cited claim that urban foxes are, on average, any larger than their rural counterparts, let alone that urban foxes are getting bigger. I don’t plan to go into any detail here (see Q/A), but the question of what controls body size in mammals is not an easy one to answer. Ultimately body size appears to be under genetic control -- genes that code for growth hormones -- but the production and release of these hormones can be influenced by external factors, such as food availability and climate, which raises the possibility that, under plentiful conditions, body size could increase. There are data from Europe suggesting that access to anthropogenic (man-made) food can increase fox and badger skull size and some rescue centres have noted that urban foxes are slightly heavier than rural ones. My own personal experience is that urban foxes typically don’t approach anywhere near the size of the animal from Kent and are, if anything, smaller than the rural ones I have come across. (Back to Menu)

Furred fox feetAppearance and Colour: Red foxes are medium-sized canids with a skull similar to that of a domestic dog, but narrower with a slender, whiskered muzzle and large pointed, erect ears. The fox has an elongated body with slender limbs and a long bushy tail (accounting for about 40% total length) up to about 13cm (5 in.) in diameter. They have light skeletons with proportionally longer hind legs than other canids, which provide them with extra propulsion when pouncing. The forepaws have five digits (four in contact with the ground and a dew claw on the back of the leg), while the hind feet have only four, lacking the dew claw; all paws are furred on the pads (left), which helps muffle their approach, prevent heat loss and provides sensory information while hunting. The pad arrangement is roughly oval, compared to the more rounded arrangement observed in many other canids, including the domestic dog (see below). The eyes are situated at the front of the skull, providing binocular vision and each possesses a nictitating (protective) membrane that moves only when the eye is closed. Vertically-slit oval pupils are surrounded by a large iris, which is slate-blue in cubs, owing to a lack of the yellow pigment lipochrome (see Breeding Biology), changing to gold/amber at around 4-5 weeks old. A layer of reflective cells called the tapetum lucidium (meaning roughly ‘bright carpet’ in Latin) sits behind the retina and reflects light back into the eye, improving vision under low-light conditions (see: Senses) and causing eye shine. Eye shine is a form of iridescence, which means that the colour of the reflected light can vary according to the angle you’re viewing it from. Nonetheless, eye shine is generally either white or blue/green when viewed head-on, or pinkish-orange when the animal isn’t looking directly at the light source.

Foxes are highly prized for the colour and texture of their fur and animals are still farmed (notably in the USA, Canada, and Scandinavia) for their pelts. In a 1986 paper to the Canadian Journal of Zoology, Daniel Maurel and colleagues, at the Centre National de la Recherche Scientifique in France, described how the Red fox coat consists of three fur types: fine underfur that traps air close to the skin, thereby providing insulation; the longer coarser guard hairs that provide water resistance and give the coat its prized sheen/lustre; and intermediate hairs, which are similar to guard hairs, but smaller (shorter and thinner). The hairs are arranged in bundles called ‘triads’; one guard hair and two intermediate hairs, associated with varying numbers of underfur hairs. The underfur covers the sides and back of the animal and is short (about 35mm, just less than 1.5 in.) and grey in colour. The guard hairs are longer, varying in length across the coat (longest on the tail), and protrude through the underfur. Coat length varies according to geography and season; in Europe and North America, northern animals have longer coats than southern animals and winter coats are generally longer than summer ones. Foxes do not sweat in the conventional sense – they have sweat glands (called apocrine glands) associated with their hair follicles, but they do not excrete water in a bid to cool the body (it has been suggested they play a scenting role). Consequently, the shortest fur covers the face (muzzle, around eyes and on top of head), ears, lower legs and paws (altogether about 30% of the animal’s surface area); heat is lost in these areas, helping the animal to cool down.

Fox tracksPelt colour is highly variable; essentially ranging from white (although most commonly yellow-red) to black. On their website, the Colorado-based Fur Commission mention 39 different colours and hues (I suspect there are more); most are the result of experimental breeding and thus exist only in captivity, but some populations (those living at high altitudes in Yellowstone, for example) exhibit some unique colouration. Occasionally some of these colour mutations are found in wild lowland populations, but it is unclear whether they arose naturally or represent animals that have escaped from fur farms. Some colour forms seem locally common and, on the Taimyr Peninsula of Siberia grey-breasted (“sivodushka”), blackish-brown (“chernoburaya”) and cross (“krestovka”) colour morphs appeared in 20-30% of the collected pelts. Fox fur colouration is under genetic control and, although many of the specifics of how the colours are inherited are still uncertain, it does seem that there are at least two genes at work on different parts of the animal’s chromosomes (see Q/A). There are four main colour phases (or ‘morphs’) found in wild populations: Red; Silver; Cross; and White. (Image: Diagrammatic representations of the foreleg paw prints of a Red fox, compared with those of a domestic dog and cat. Note the arrangement of canid paws differ from those of felids and the pads of the fox track generally do not intersect as in dog tracks, although the quality of the track depends on the ground conditions.)

Red fox morphRed is the most common colour morph, although there are many hues, varying from reddish-yellow to very dark red/orange, with varying amounts of black interspersed. The coat colour comes from pigments called melanins that are deposited in the hair as it grows; the ratio of light (phaeomelanin) to dark (eumelanin) pigment and the order in which they’re laid down in the hair determines the exact colour. Guard hairs have bands of black, yellowy-brown and white (no pigment) present at varying concentrations across the body, causing blended colouration. In his Wild Guide, Simon King notes that many of the red guard hairs have a red base, dark centre and a red (or occasionally creamy white) tip. Red foxes have varying amounts of black fur around their eyes, the side of the muzzle, on the back of their ears and on their lower legs (often called ‘socks’). A darker patch of hair near the base of the tail (over the supracaudal scent gland) is also evident in many individuals; this area lacks underfur, having only guard hairs with thick white ends and black tips. A white ‘bib’ that extends up to cover the bottom jaw and lower half of the muzzle is common, while the lips and nose are generally brown. The fur on the belly ranges from white to slate grey and the tail is often less colourful than the body. There are occasional reports of ‘black-bellied’ foxes -- which have dark red backs and dark grey/black sides and ventrum (belly) -- and, writing in 1954, Tarvo Oksala found that 18 (0.6%) of the 3,000 Finnish fox skins he examined were of this type. There are no equivalent data from Britain but, in his 1968 book Wild Fox, Roger Burrows mentioned that black-bellied animals have occasionally been caught by hunts here, including in Hampshire, Gloucestershire and Shropshire.

Cross foxes are very similar to the normal Red morph, but have a dark brown or black line that runs along the back to the base of the tail and a second line running across the shoulders and down the legs; this forms a cross pattern at the shoulder. Cross foxes are found throughout Europe (recall the subspecies crucigera, or ‘cross-bearer’, described from Germany) and common in North America, presumably testifying to the spread of foxes introduced from Europe by early settlers. The bulk of foxes (about 60%) fall into the Red colour morph, with Cross foxes accounting for about 25%.

The degree of melanism is greatest in the Silver foxes; this is the earliest documented wild Red fox colour morph. The coat is black, with varying degrees of white ‘frosting’ that comes from banding of the guard hairs; eumelanin is deposited in the body of the hair and causes it to appear black, while phaeomelanin is deposited further up, giving a paler tip. The degree of silvering is highly variable as phaeomelanin deposition varies across the body and between individuals; some foxes will be jet black, while others can appear slate grey. There are several mutations of the silver morph, one of which (the Alaskan silver) has a browner tint to its coat. Melanism is more common in cold climates (often being highly localized), so silver foxes are more common in northern regions, particularly in the forest zones and forest-tundra belts of middle and eastern Siberia (it’s rare in desert and steppe populations). Overall, silver foxes account for about 10% of colour morphs. Jet black foxes are, however, very rare in Europe; in his 2005 Carnivores of the World, Ronald Nowak notes that such foxes are confined to the extreme north of Europe and make up about 1% of the population.

Silver Fox   Cross Fox
The Red fox comes in an impressive range of colours (called 'morphs'), including various degrees of melanism. Melanistic foxes range from jet black, or black with a sprinkling of silver-tipped guard hairs (so-called 'Silver' foxes - above, left) to cross foxes (above, right), which have various proportions of black and orange fur according to their genetic make-up.

Black (melanistic) foxes are occasionally seen in the UK; being genetic variants, they crop up from time-to-time with Red cubs in litters. In September 2008 a young black fox was filmed in a cemetery on the outskirts of Chorley in Lancashire (north-west England) and the BBC’s SpringWatch team filmed a black fox in a garden in southern England in early June 2010; posts on the BBC forums suggest several black fox sightings from around the UK during 2010, including in Hockley (Essex), Crawley (West Sussex), Paisley (Scotland) and Clee Hill (Shropshire). I have also received several e-mails from readers who have seen black foxes, the most recent being an animal spotted in Llanelli, Wales during May 2010. There was also a report of an adult fox with three cubs -- on red and two black -- in Abingdon, Oxford during June 2011. The most recent black fox sighting from Britain that I know of was an adult vixen photographed by John Moore in a field in the Cambridgeshire village of Bassingbourn on 26th March 2012. Interestingly, looking at the photos that John sent to ITV News, the animal has the long, fine coat typically associated with North American animals and particularly typical of fur farm foxes – it makes me wonder whether this animal was an escaped pet. Unfortunately, the animal was killed by a car three days later on a road in Bassingbourn, Cambridge, but is now being studied by scientists at the Anglia Ruskin University.

Work on farmed foxes has found that the degree of melanism is related to temperament. The late geneticist Clyde Keeler demonstrated that, because melanin and adrenalin are generated via the same hormone ‘pathway’, black foxes tended to have higher adrenalin levels and be less fearful than lighter coloured animals. Indeed, in a 1970 paper to the Journal of Heredity, Keeler and his colleagues described pure-bred Red foxes as “a bundle of jangled nerves”. There is also some indication that silver and red morphs may have some physiological differences; working in Poland, Wlodzimierz Nowicki found that farmed Silver foxes had smaller arteries in their cardiac circulation than wild Red foxes, although it is unclear whether this has arisen during the selective breeding process.

Very occasionally white Red foxes are reported from the wild; both albino and non-albino animals have been documented. In their Mammals of the Soviet Union, Vladimir Heptner and Nikolai Naoumov note that white (or “de-pigmented” as Heptner and Naoumov call them) foxes are rare and that such animals most often appear in the southern forest zone of region. Interestingly, Heptner and Naoumov also mention that albinism usually develops in foxes after years of insufficient food, although it’s difficult to see why this should be so, given the genetic basis for the condition.

Albino Red Fox cubIn his 1968 book Town Fox, Country Fox, Brian Vezey-Fitzgerald notes that white individuals have been reported from Britain, the majority from Devon; that said, he notes that five were apparently caught at Whaddon Chase in north Buckinghamshire, although some maintain that these were ‘cream’ rather than white animals. In his 1896 A Handbook of British Mammals, Richard Lydekker notes that a white fox was killed in west Somerset by the Taunton Vale Hounds in 1887, while Colonel Talbot, in his 1906 Foxes at Home, described a white fox caught in Wentworth, Surrey during the late 1800s. Similarly, in his 1906 book, The Fox, Thomas Dale refers to a white fox seen in Roborough Woods, Devon during 1898, another in Essex and two in Somerset. In a brief note to Imprint, the journal of the Doncaster Museum and Art Gallery, during 1985, Colin Howes reviewed the hunting literature for cases of white foxes in Yorkshire. Mr Howes found that a white fox was taken by the Cleveland Hounds in Eston on the North Yorkshire coast during the late 1800s, while “a very white fox” was apparently flushed by the Bramham Moor Hunt on a couple of occasions in the Hutton Thornes area, just west of York. Finally, Mr Howes notes that a “totally white” fox was killed at Hawthorne Bank, near Aldwark north-west of York during 1863. Elsewhere in the scientific literature, an account of a number of white foxes in the countryside below the Cheviot Hills appeared in the 1949 issue of the Journal of the Zoological Society of Scotland, but I currently have very few details on this report. More recently, in April 2006, a white fox was seen several times on National Trust land in Thurstaston on the Wirral Peninsula, another reported from Kensington, London during November 2009, one seen in an urban area of Derby in November 2010, and one reported by a farmer out lamping in Lincolnshire during late October 2011. Two white, non-albino, foxes were shot in on a farm in Kent during November 2011 and, in May 2012, a white fox was photographed on a farm in Bethersden, Kent. The most recent encounter I'm aware of was an unconfirmed report of a white fox on an industrial estate in Bournemouth (Dorset, UK) during mid-November 2012.

It is worth noting that not all cases of white foxes recorded from Britain were Red foxes. Dale mentions a white fox seen in Kincardineshire, on the coast of north-east Scotland, which was believed to have come ashore from the wreck of a Norwegian vessel and was probably an Arctic fox. Similarly, in 1984, Don Jeffries at the Nature Conservancy Council and Institute for Terrestrial Ecology biologist Robert Stebbings published a short paper in the Proceedings of the Dorset Natural History and Archaeological Society about a “strange light-coloured fox” spotted in Dorset, south-west England. The animal was seen on several occasions on a farm near Poole during April 1983, before it was found (recently) dead in a field about 1km (just over half-a-mile) away, on 16th April. The body was handed to the authors for identification and autopsy and turned out to be a young female Arctic fox (Vulpes lagopus) that had died from internal bleeding, apparently caused by a blow to the chest. The authors point out that this animal obviously did not arrive from the arctic under its own steam and so had presumably escaped (or was illegally released) from a private collection or zoo.

In most cases, foxes fall into one of the aforementioned colour morphs, but some may exhibit combinations of colour patterns or hues. Red colouration with large white patches on the head (i.e. piebald), for example, is well documented, as are white (rather than the usual black) ‘socks’. Vezey-Fitzgerald mentioned a piebald fox that was killed by the Taunton Vale Hunt in Somerset during the 1880s and, more recently, a lady e-mailed me to describe a brindle-coloured fox she saw while out walking her dogs near Southampton in April 2011; she described it as having “vertical stripes the whole length of the body, fairly wide apart, black on very dark 'yellow'”. Similarly interesting patterns have been reported from North American foxes, including a fox run-over near Yellowstone’s Tower Junction during 1998 that was largely (about 60%) black, with patches of red. Golden foxes are also reported from time-to-time; these have a yellow/blonde coat, similar in hue to Golden Labrador dogs – a family were reported from Stoborough Heath, near Arne in Dorset (UK) during May 2011 and again in the summer of 2012. A four-week old male cub was found in Flackwell Heath near High Wycombe in Buckinghamshire at the end of April 2011 and was taken to St Tiggywinkles (a wildlife hospital based in Aylesbury); the cub had very light blonde (bordering on white) fur.

A very common feature among all colour morphs of foxes is a white -- occasionally black or grey -- tip (or ‘tag’) to the tail. This tip is noticeable on the cub’s tail even before it is born (by around 46 days into gestation) and, in adult British foxes, covers about 10cm (4 in.) of the tail. The tail tip is often larger in North American foxes and, both there and in Europe, northern animals tend to have longer white tips than southern animals. In a brief paper to the Proceedings of the Zoological Society of London during 1963, Gordon Corbet discussed the frequency of white tail tips among British mammals. Corbet looked at skins kept at the British Museum and found that 11 (73%) of the 15 skins from England and Wales, and 27 (87%) of the 31 collected from Scotland had a white tip to the tail, giving a total occurrence of 83%. In his paper, Corbet noted that the hairs were albino (i.e. devoid of any pigment) and that, among foxes: “a white tip is normal but by no means universal”. Many early authors and countrymen maintained that it was possible to sex a fox based on the tail tip; the white tip was considered to be indicative of a male. This is not the case and either sex can possess a white tag.

Samson foxA final note on the variation in coat appearance should include aberrations. In rare cases, a fox may lack some or all of the guard hairs and possess underfur that is tightly curled, giving a ‘woolly’ appearance; these animals are Samson foxes (photo, left). It should be noted that Samson isn’t a species of fox; it is a genetic condition affecting several different fox species, including Red, Arctic and Grey foxes. Samson foxes are well known from fur farms (where their pelt is almost valueless) and have occasionally been recovered from the wild. Early naturalists considered that the Samson condition was caused by a parasite or poor diet, but breeding studies by Finnish biologist Tarvo Oksala during the late 1940s and early 1950s suggested that it is an unstable recessive genetic trait, meaning that it can be inherited, but normal foxes may moult into Samsons and vice versa. According to several authors, Samson foxes are larger than normal foxes and tend to live around human settlements where they feed largely on rubbish; they also carry more fat, have faster metabolisms and shorter claws than normally-furred animals. I am not aware of any Samson foxes having been seen in the UK, but wild individuals have been shot in parts of northern Europe, including Finland, Sweden and Norway as well as in the USA. (For more details, please see the Q/A: What is a Samson fox?)  Occasionally, completely hairless animals are spotted. Some diseases (mange, malnutrition and hypotrichosis, for example) can cause hair loss, but in these cases it seems that the hair follicles are missing from the skin; these are alopecic foxes.

It is debatable whether foxes undergo one or two moults per year and many authors simply consider them to have a single, protracted moult each year (lasting for much of the summer). Maurel and his team, however, described two moults in his French foxes: a spring moult where the old winter coat was lost and an autumn moult during which underfur grew in. The foxes started shedding in early April and the coat lost its lustre; by the end of the month new growth had started at the base of the legs. New hair growth progressed up the legs and, by the end of June, the summer coat completely covered the legs, abdomen and flanks; growth on the back and tail was complete by late August or early September (this was the summer coat) and then there’s something of a hiatus for a month-or-so. During October and November, Maurel and his colleagues recorded growth of some of the fine (underfur) hairs that hadn’t grown during the summer – this thickened up the coat in time for winter.

Red Fox Moult sequence
The seasonal moult pattern of the Red fox. The light grey indicates the progression of the summer coat, while the dark grey areas show the progression of the winter coat. The star at the beginning of April signifies the first time that hair is shed. Diagram originally published Daniel Maurel and colleagues in the Canadian Journal of Zoology during 1986 and is reproduced here with permission from the publisher.

In Britain and Europe, the coat is in best condition from about November to February. Some foxes may begin to moult in late February, but most don't start until April and the protracted nature of the moult can lead to a "piebald" appearance during much of the spring and early summer. Often, breeding vixens begin to moult before barren vixens or males and can look very ‘tatty’ or ‘mangy’ for much of the late spring. From late January or early February the hairs become brittle and the tips begin to break, so the coat begins to lose its condition and worn patches may become apparent on the back and rump. Hormonal studies on fur farm foxes have demonstrated that the moult is controlled by endocrine glands and stimulated by light such that altering the photoperiod (i.e. making the day appear longer or shorter) can cause the moult to speed up or slow down accordingly. Some reports suggest that a warm autumn can delay moulting by a week-or-two, while an early frost accelerates it. Interestingly, there is some evidence that the moult progresses differently in silver foxes; one 1948 study documented a single, spring, moult that started at the rear and moves forward. (Back to Menu)

Distribution: The Red fox is the most widespread of all wild canids and has the largest natural distribution of any non-human land mammal. The distribution of the fox covers an estimated 70 million sq-km (~27 million sq-mi) and includes a diverse array of habitats from deserts to Arctic tundra. The distribution of the Red fox can be summarised as being Holarctic, Oriental, Australasian, Northern Neotropical and African. In other words, these foxes are found throughout the UK and Europe east through Russia, Kazakstan, Iraq, Iran, Pakistan into northern India, China and Thailand to Japan. To the west, Red foxes are found in the northern and eastern USA, north through Canada and Alaska to Baffin Island; they’re conspicuously absent from many of the Arctic islands including Greenland and Iceland. Within Eurasia, it appears that the severity of the winter (i.e. the lowest temperature) limits the northern range of the Red fox. This species doesn’t appear to have spread far into the African continent, although it is found on the northern fringes (north Morocco, Algeria and Tunisia) and down through eastern Libya, western Egypt into northern and central Sudan, roughly following the course of the River Nile. They are also absent from much of the southern and western USA, Mexico and most of the Southern Hemisphere. Where Red foxes are absent they are typically replaced by other fox species, including the Fennec (Vulpes zerda) and Cape fox (Vulpes chama) in Africa, the Gray fox (Urocyon cinereoargenteus) in most of southern North America and six species of ‘Zorro’ foxes (Lycalopex spp.) in South America.

At the far north of their range Red foxes are replaced by the Arctic fox (Vulpes lagopus) and, where the two species meet, it appears that Red foxes are dominant and displace the smaller Arctic species. Indeed, in his 1987 book Running with the Fox, David Macdonald noted that the northern range of the Red fox is set by food availability, while the southern range of the Arctic fox is set by the northern range of the Red. Red foxes are generally absent from Arctic tundra because their metabolisms are higher than that of the Arctic fox; they thus require more food than the high Arctic winter can provide. Experiments on captive Arctic foxes in 1950 showed their metabolic rate only began to rise when external temperatures dropped to between -45 deg-C and -50 deg-C (-49 and -58 deg-F) and they only began to shiver after more than an hour at -70 deg-C (-94 deg-F). The equivalent data for Alaskan Red foxes in winter pelage (published in 1955) demonstrated that their metabolism started to rise at -13 deg-C (8.6 deg-F) and had almost doubled by -50 deg-C. As well as the Arctic, Red foxes also penetrate into the Middle Eastern deserts, although these animals are considerably smaller (averaging 3kg / 6.6 lbs.) than those in Europe.

Red Fox Distribution
The approximate global distribution of the Red fox (Vulpes vulpes)

Red foxes were introduced extensively to North America by early European settlers and Brian Vezey-Fitzgerald, in his 1960 book Town Fox, Country Fox quoted General Roger Williams (the Master of the Iroquois Hunt in Kentucky) who, writing in 1904, said:

The red fox was unknown in America previous to 1760, at which time a number of them were imported from England and liberated on Long Island in New York.”

Some authors suggest the release was made by one of the first English governors of Long Island, although several early writers (during the early 1600s) mention black foxes -- even buying these animals from Indians -- but say nothing of red animals. In his 1980 book Red Fox, Huw Lloyd notes that subsequent introductions were made in Maryland, New Jersey, Virginia and several other eastern states – circumstantial evidence suggests this was in response to an absence of foxes in the area. Whenever and wherever they were first released, these foreign imports spread rapidly westwards across most of lowland northern North America, as forests were cleared, seemingly to the detriment of the native stock, which now only survive in isolated pockets, primarily at high altitudes (see Q/A).

Australian Red fox distributionAustralia has also seen its share of Red fox introductions, with animals released to provide sport (rather than rabbit control) by home-sick expatriates who formed the Acclimatisation Society of Victoria; they have arguably caused more serious ecological problems here than anywhere else. In his 1987 book, Macdonald notes that the first confirmed importation of foxes to Australia was the English animals released by T.H. Pike onto his property near Keilor in Melbourne, Victoria (on the south-eastern tip of the island) during 1845. According to Macdonald, two males were subsequently released near Sydney in 1855 and, in 1864, a male and two females arrived on a ship from Suffolk and were released by the Melbourne Hunt Club. It appears, however, that most of these initial releases failed to ‘take’ and it wasn’t until almost a decade later that introductions began seeing success. It is now widely considered that the present Australian fox population was founded by two shipments liberated in Victoria: one consisted of two foxes released by Dr King near Ballarat in 1871; the second was about five animals released on Point Cook, in the Werribee-Geelong district of southern Victoria, by Mr T. Chirnside in the early 1870s. By 1880 the species was widespread in Victoria (especially between Geelong and Melbourne), but hadn’t moved far outside the region; it was at this point that the colonization gained momentum. In a paper to the journal Mammal Review during 2010, Glen Saunders -- at the New South Wales Department of Industry’s Vertebrate Pest and Weed Unit -- and two colleagues told the story of how the Red fox spread across Australia. The species crossed the south Australian border in 1888, reached New South Wales (NSW) in 1893, and Queensland and Western Australia early in the twentieth century. The rate of movement was particularly rapid (up to 160km/108mi per year) in the inland saltbush and mallee country, and there is some evidence that the spread was actively assisted by humans. Foxes now occupy all of continental Australia except for the northern arid and tropical regions, at least 18 offshore islands, and even penetrate into the hot deserts of the interior when seasonal conditions permit. Foxes were illegally released on to Tasmania during the late 1990s, although the population didn’t become established until 11 animals were deliberately released in three areas of the island in late 1999; carcasses have been found here since 2001. There is currently no evidence of foxes in New Zealand and it has been illegal to import them there since 1867. (Image: Distribution of the Red fox in Australia 2006/2007. One of the National Fox Maps produced by the Invasive Animals CRC and Australian Government, published in: West, P. (2008). Assessing invasive animals in Australia 2008; available from feral.org.au. Map copyright of the Commonwealth of Australia and reproduced here with permission.)

At the pinnacle of the last ice age, global sea levels dropped by about 120m (almost 400 ft.) and this exposed a ‘land bridge’ that enabled animals to move freely between Britain and the European continent until it was flooded about 6,500 years ago as the ice began to melt. Fox numbers no doubt waxed and waned in post-glacial Britain and early hunting literature suggests that foxes became more numerous and widely distributed between about 1750 and 1850, with a further population and range expansion between 1950 and 1965. Indeed, it was during the 1950s that the Red fox expanded its range in Scotland and it has been suggested that the abundance of rabbits dying from myxomatosis permitted this colonization, although some have argued that initial establishment occurred before the first myxomatosis outbreaks and was linked with the planting of conifer forests. Regardless, in 1973, Hugh Kolb and Raymond Hewson suggested that, as rabbits disappeared from much of the countryside, foxes were forced to disperse looking for food (aiding further colonization) and, as vole numbers began increasing in the absence of rabbit grazing, fox populations stabilised.

Red foxes are now common throughout mainland Britain and Ireland, where they’re generally considered native -- this is despite there apparently being no evidence of Red foxes in Ireland prior to the arrival of humans (and hence the suggestion by some that they were imported for their fur in pre-historic times) -- and have been introduced to several islands. This species is absent from all of the Scottish islands except Skye, where they were illegally introduced, and from the Channel Islands and the Isles of Scilly. In their contribution to the 2008 Mammals of the British Isles: Handbook 4th Edition, the Bristol University biologists note that foxes are also present on the Isle of Harris, having been illegally introduced. Scottish Natural Heritage, however, tell me that despite occasional reports of foxes from the island, none have ever been confirmed and no signs have been found by the army of mink trappers that operate on Harris. Foxes have experienced a tumultuous history on Anglesey; they were relatively abundant until some point during the mid-1800s when they appear to have died out and the island remained devoid of foxes until three animals were released near Holyhead during August 1960. Anglesey’s foxes kept a low profile until the late 1960s, when complaints of poultry losses caused them to be hunted; despite intensive fox control throughout the 1970s, the population remained stable. Along the south coast of England, foxes are absent from Brownsea Island despite the strong population at nearby Sandbanks; the National Trust rangers there have never had a confirmed case of a fox from the island, although there are occasional reports of brief sightings, the most recent being about ten years ago. Foxes were introduced to the Isle of Wight in 1845 to provide sport (the Isle of Wight foxhounds were also established in this year) and the establishment of the population was in no small part the work of huntsmen Ben Cotton and Henry Nunn; foxes are now widespread and common on the island.

On some of Britain’s islands, the status of the fox is less clear-cut and the situation on the Isle of Man is a good example. There is no archaeological evidence that the fox is native to Man, although there is some evidence that they were present in small numbers during the mid-19th Century, with the first report being an animal killed at Lezayre in the north of the island during November 1861. The foxes of Man kept a low profile until 1986, when four adults were apparently released into the Santon Valley, in the south-east of the island, and then again in 1990, when biologists David Macdonald and Elizabeth Halliwell found a litter of cubs in the same region. In a 1994 paper to the journal Global Ecology and Biogeography Letters, Macdonald and Halliwell used various factors (e.g. landscape maps, prey densities and distributions, and faecal counts) to estimate that there were between 120 and 300 animals on the island in 1990. It soon became clear that this was probably a considerable over-estimate and, in a 2003 paper to Mammal Review, Game Conservancy Trust biologists Jonathan Reynolds and Mike Short reassessed the situation, concluding that there were likely to be no more than 15 animals across the entire island. Indeed, the researchers noted that foxes may be entirely absent from the island, although there are occasional (unconfirmed) reports from residents. Most records are held by the island’s Museum of Natural History, but record coordinator Kate Hawkins told me that reports are rare and there have been very few since 2002 – the most recent credible report made to her was of droppings discovered in a suburban park in the south of the Isle of Man during November 2009. The Senior Biodiversity Officer on the island, Richard Selman, tells me he receives about one fox report per year, of variable credibility -- the most recent reliable report being from Ballure, on the edge of Ramsey, in December 2010 -- but is of the opinion that there are, at best, only a handful of foxes on the island.

Red fox on OrkneyThe situation on the Orkney Isles, off the coast of Caithness, northern Scotland is similarly unclear. In 1936 a pair of foxes were released in the Ysenaby area of Sandwick, West Mainland (Ornkey), but were found dead a few months later. Since then, there have been several reports of foxes 'at large', but none have ever been confirmed. On 12th December 2007, however, a seven-month old male fox was found dead on the roadside at Holm straights between Fea and Cannigal (Orkney) by a gentleman on his way to work (photo, right). Post-mortem analysis revealed that the animal died from blunt-force trauma to the head (having probably been hit by a car) but was in otherwise excellent condition, with pristine teeth and claws. Naturalists Chris Booth and Richard Matson summarized the status of the Red fox on Orkney in a short paper to the Orkney Field Club Bulletin during 2008, concluding that the animal had escaped (or been released) from a private collection and had spent no more than a couple of days in the wild. The Orkney Isles are currently considered fox-free. At the time, there were rumours that the fox was deliberately planted as a hoax, rather than an escaped pet accidentally run-over. There is, as far as I know, no proof that it was a hoax, but such activities aren’t unknown – a fox believed to have been caught in a snare elsewhere was dumped on a road in the south of the Isle of Man during 1990, and the carcass of a fox found on Shetland in 1996 is also believed to have been a hoax. (Back to Menu)

Habitat: Red foxes thrive in almost all habitats because they are relatively unspecialised in their way of life. Consequently, foxes have been found at most altitudes, from sea level up to 3000m (almost 10,000 ft) and in most terrestrial environments on Earth; their distribution and abundance is a result of the availability of food and suitable breeding sites. Red foxes are generally a species of, and do best in, mixed landscapes consisting of scrub, woodland and farmland. Red foxes are found in dense woodland and plantations, on moorland, coastal dunes and above the tree-line in mountain ranges, but the reduction in (or high seasonality of) food supply in such places tends to mean they are less abundant in such habitats. Indeed, it is widely held that the clearance of woodland to make way for agricultural land created very favourable conditions for Red foxes and, in conjunction with the introduction of game species (e.g. brown hare, rabbits, pheasant, domestic fowl, etc.) to these habitats, is largely responsible for the rapid colonization of Eurasia and North America by this species.

In 1980, M.A.F.F. biologist Huw Gwyn Lloyd wrote of the habitat of the fox:

Areas least suitable for foxes, whether harassed or not, would have some or all of the following characteristics; flat, open country; few woodlands or very open deciduous woodland; neat or simple field boundaries (fences or ditches, e.g.); no scrub or uncultivatable land; large field, mainly arable and a high water table.

Red fox in urban gardenIn plantations, foxes prefer a mosaic of close-canopy conifers (which offers shelter) at the pre-thicket stage (which provides food) – once the canopy has completely closed, the productivity of the plantation declines and, if used by foxes, it now serves only as a denning or daytime resting site. In general, foxes tend to use mature conifer plantations as daytime resting sites, moving into nearby open areas to feed. The use of the habitat will also vary seasonally. In Tuscany, central Italy, Paolo Cavallini and Sandro Lovari found that foxes showed a preference for marquis (scrubwood) habitats, meadows and pine forests, with the former being most (and the latter least) used during cold seasons. There are many accounts of foxes focusing more time and energy on coastal and dune habitats during seabird breeding seasons. Similarly, observations by David Macdonald in Oxford have shown that on warm, damp nights foxes can spend several hours searching livestock fields for worms, while in hot, dry conditions they focus their attention more heavily on small mammals in woodland or crop stands.

Foxes thrive in many urban areas and it is in streets, back gardens and parks that most people will encounter a fox nowadays. Indeed, Mark Cardwine gives the Red fox the accolade of ‘most urbanized canid’ in his 2007 book, Animal Records, having adapted to life in towns and cities more successfully than any other member of the dog family (presumably excluding domestic pooches). Under the definition argued by Robert Francis and Michael Chadwick in their 2011 paper to Applied Geography, the Red fox is a truley synurbic species; their population densities are higher in urban areas than in rural habitats. As a testament to their comfort around urbanization, a fox has even been reported to have raised a litter of cubs in the 54,000-seater Yankee Stadium in New York!  In Britain, however, foxes tend to do best in middle-class suburbs with low density housing where most houses are privately-owned and accompanied by a reasonable size garden that is largely free of disturbance. In a 1986 paper to the Journal of Animal Ecology, Bristol University biologists Stephen Harris and Jeremy Rayner suggested that, in Britain, the boom in private house construction after 1930, which occurred as increased mobility allowed people to live and work further apart, led to a proliferation of privately owned three-bedroom semi-detached houses that appear to offer foxes just what they need.

Contrary to popular misconception, urban foxes aren’t the preserve of Britain – they’re now present in most large European cities and are also found in cities across America (including Los Angeles, New York and Washington), Australia (Adelaide, Brisbane, Canberra, Melbourne and Sydney), Canada (Toronto) and Japan (Hokkaido and Sapporo). Despite being called urban foxes, it is a misrepresentative to think that these animals are confined to built-up areas. Tracking studies by Bristol University have shown that urban foxes move freely into and out of the city while feeding and looking for mates; some rural-based animals were tracked moving into the city at night to feed. Similarly, in a 1982 paper on the distribution and ecology of urban foxes, Oxford University zoologists David Macdonald and Malcolm Newdick found that dispersing foxes moved back and forth between town and country, and they concluded:

A categorical division between rural and urban foxes was found to be without foundation. The proportion of urban and rural habitats embraced within the home-ranges of foxes varied from one to the next, and foxes moved readily between them.

A recent review of Red fox distribution reported that there are 'significant numbers' of foxes living in an estimated 114 cities across the globe, including 56 in the UK, 40 in mainland Europe, 10 in the USA and six in Australia. For more information about when and why foxes colonised our towns and cities, please see the associated Q/As. (Back to Menu)

Abundance: There are no estimates of the global population of Red foxes, although they are widely considered to be the most populous wild canid. The number of foxes in a given area is controlled by several factors (see Q/A), although three seem particularly important: food availability; suitable den sites; and predators/competitors (particularly other larger canids such as coyotes and dingoes). In some areas populations are regulated by social factors, although this tends to be only when other factors (e.g. food) aren’t limiting. Similarly, the severity of the winter has been shown to impact fox abundance, with the milder winters at lower latitudes supporting larger fox populations. The percentage of open areas also influences fox density, with fewer foxes in dense forests (i.e. those with 80% or more tree cover) and numbers increasing as the percentage of open land increases. According to one Russian study, the spread of foxes seems to be favoured by forests with 30% to 60% open areas. In short, fox populations aren’t uniform; instead they vary according to the hospitality of the local environment.

Fox abundance varies with habitat, with the lowest densities (fewer than one animal per sq-kilometre) found in conifer forests/plantations and open fields. Densities are higher in deciduous woodland and on agricultural land (1-2 per sq-km), with yet more in the suburbs (2-3 per sq-km) and the highest densities (4 or more per sq-km) in urban areas, particularly large cities. There is considerable variation and densities of three foxes per sq-km may be found in highly productive mixed farmland.

The British fox population also shows considerable variation in abundance according to habitat, with densities generally ranging from about one fox per four sq-km, to four (or more) per sq-km; the average is about two animals per sq-km. In a paper to the Journal of Zoology during 2000, a team of biologists at the Game Conservancy Trust in Hampshire presented pre-breeding density estimates of 0.41 fox per sq-km, 1.2 per sq-km and 0.16 per sq-km for rural mid-Wales, east Midlands and East Anglia, respectively. There are, however, extremes – from one breeding pair per 40 sq-km (15.5 sq-mi) in hill areas of Scotland, to the largest population density ever recorded (37 foxes per sq-km) in Bristol city during the early 1990s. The Pitsea Landfill site in Essex that recently featured on the BBC’s SpringWatch boasts a high density of foxes – a student who looked at fox dynamics on the site on behalf of the resident naturalist, Phil Shaw, estimated a density of one fox per eight hectares (approximately 12.5 foxes per sq-km, or 32.4 foxes per sq-mile). Again, this illustrates how a readily available food supply can significantly influence fox abundance.

In 2007, Polish mammalogists Kamil Barton and Andrzej Zalewski surveyed the literature on fox populations in Eurasia and found that winter density ranged from 0.001 to 2.8 animals per sq-km, with an average density of 0.21 per sq-km. In other words, the range was one fox per 1,000 sq-km (386 sq-mi) to almost three foxes per sq-km, with an average of one fox per five sq-km (2 sq-mi). In northern Europe densities are typically one fox per three-or-five sq-km while, in Spain, densities are around one fox per three-quarters sq-km.

Red fox in snow storm
The severity of the winter seems to limit the abundance of foxes across Europe and Asia. As you progress northwards, fox density reduces (i.e. each fox holds larger territories, so there are fewer foxes in a given area) presumably because finding food where snow cover is often deep and ground frozen is more difficult.

Generally-speaking, the highest stable fox densities are found in the most heterogeneous (diverse) habitats, so urban and arable areas can support two-or-more foxes per sq-km, while relatively barren upland regions rarely exceed one fox per five sq-km. Indeed, a recent paper to the journal Acta Theriologica by German biologists reported fox densities in settlements that were three- to eight-times higher than those in "strictly rural" of southern Germany. In homogenous (uniform) habitats, densities can be high, but are more prone to cyclical fluctuations in accordance with prey. How prone to fluctuation a fox population is depends on the species on which it can feed. In heterogeneous habitats foxes can switch to a different species when one declines; this is not the case in homogenous habitats where voles are often the main (sometimes only) source of food, so fox populations fluctuate with the number of voles. There are occasions where homogenous habitats can sustain high fox densities. Working in Sweden during the late 1960s, for example, Jan Englund found that fox populations in southern areas, where rabbits were found, were steadier in number and breeding success than those in northern areas, which are dominated by rodents.

The data on fox abundance in North America is patchier than for Europe. There are, as far as I know, no recent estimates (most sources refer to those given by Dennis Voigt in 1987), but those that do exist suggest that fox density typically ranges from one animal per ten sq-km (4 sq-mi) in less productive areas (arctic tundra and boreal forests, for example), to one animal per sq-km in more productive agricultural landscapes. Locally, however, densities may be higher, with an estimated ten animals per sq-km on Round Island, Alaska in 1989. In a 1991 paper, Rick Rosatte and colleagues estimated the fox population of metropolitan Toronto to be about 1.3 animals per sq-km. In much of North America coyotes (Canis latrans) are an increasingly common sight in urban areas; coyotes are known to displace foxes and their presence could account for lower fox densities here than in urban Britain.

Total numbers are far more difficult to estimate than population density; hence few attempts have been made. Several local estimates exist, although most are rather dated now. A study of the New Forest, during May 1974, estimated there to be 592 animals in an area of 271 sq-km (about two foxes per sq-km). The most recent published census (conducted between 1999 and 2000) estimated that Britain has a stable population of around 230,000 animals (before cubs are born); a further 150,000-or-so are estimated to be in Ireland. In 2011, the ‘official’ urban population guestimate stood at about 33,000 animals, although this was calculated in the 1990s and recent media articles have quoted figures higher than this. Indeed, a survey of more than 11,000 respondents from across the country -- completed as part of the recent Foxes Live series shown on Channel 4 during May 2012 -- led Dawn Scott at Brighton University and Phil Baker at Reading University to an estimate of 35,000 to 45,000 foxes living in urban Britain. Dr Scott informs me that they are planning to publish a more detailed analysis of the survey data later in 2012. To the best of my knowledge, there are no estimates of the total European population, nor of that in North America. In Australia it is equally difficult to assess fox numbers because the diversity of habitats and seasonality is arguably greater than in the UK; that said, estimates of 7 million animals have been put forward! Australian fox biologist Clive Marks told me that:

The Australian environment is so variable in habitat and habitats change in carrying capacity due to season and drought/boom and bust cycles etc making any one figure meaningless; much more than for the UK I would guess – that is not subject to extreme changes.

Indeed, density estimates for Australian foxes are ordinarily restricted to simply ‘rare’, ‘common’ or ‘abundant’, although some figures have been published. In a 2006 report by Natural Resources and Water (a department of the Queensland government), Matt Gentle of Biosecurity Queensland wrote:

Studies in Australia have shown that fox density varies considerably by habitat. Densities range between 0.9 foxes per km2 in arid areas, between 1.2–7.2 per km2 in fragmented agricultural habitats, and up to 16 per km2 in urban areas.”

Data compiled by the Invasive Animals Cooperative Research Centre for 2007 (see map above), suggest that foxes are most abundant in the south (particularly the south-east, around the Eyre Peninsula, Port August, Adelaide etc) as well as parts of New South Wales (including Ivanhoe, Sydney, Cooma and Gunnedah).

See associated Q/A for more details on how we estimate fox numbers. (Back to Menu)

Fox tooth sectionsLongevity: Over the years, various methods have been used to try and estimate fox age, including the weight of the eye lens, general dental development (i.e. tooth eruption), tooth wear, baculum (penis bone) development, cranial measurements and tooth sectioning. In a 1978 paper to the Journal of Zoology, Bristol University biologist Stephen Harris (at the time based at Royal Holloway College in Surrey) compared the effectiveness of various different techniques on a sample of 336 foxes killed in London between 1971 and 1973. Harris found that visual inspection of the baculum could separate juvenile and adult males (obviously of no use for females), but no separation of year classes was possible. Similarly, the weight of the eye lens -- which grows throughout life but experiences very little wear -- could separate yearlings from adults (91% with lenses weighing less than 210mg were less than a year old), but thereafter there was too much overlap between age classes to be reliable. Harris also found that tooth attrition (wear) could be used effectively in some populations (93% of the sample up to four years old were correctly aged this way), but was a highly variable character -- it’s heavily related to the diet of the animal in question, and tooth wear is slower in old age -- and was thus not a reliable method of assessing absolute age. Overall, Harris concluded that:

None of the measurements of growth (baculum weight, eye-lens weight, skull and skeletal measurements) proved of any absolute value for age determination in the present study…

Harris found that the most effective method of ageing foxes was to use incremental lines of cementum. Cementum is a bone-like connective tissue that covers the root of a tooth, providing protection, support and a connective surface for fibres that attach the tooth to the jaw bone; it’s laid down throughout the animal’s life with heavily mineralized layers (incremental bands) alternating with those less mineralized (incremental lines). The result is that, if you cut the tooth into sections and dye it, the tooth has a ‘banded’ appearance, with incremental lines showing up as light strips. Exactly why mammals deposit these light and dark bands is unknown, although there are several theories, including that lack of food and a harsh climate cause compacted (dark) layers of cementum to form (the “environmental effect”), and that they’re associated with physiological changes during the breeding cycle (the “endogenous effect”). Either way, the idea is that you can count the tooth rings, like you would the rings of a tree, to determine its age. (Image: Three Red fox tooth cross-sections showing how staining highlights incremental bands, allowing an estimate of the animal's age.  Photos courtesy of Dr Jonathan Reynolds at the Game and Wildlife Conservation Trust.)

In a study published in the Danish Review of Game Biology during 1968, Birger Hensen and Lise Nielsen were the first to establish counting cementum rings as a method for ageing foxes. Hensen and Nielsen’s method involved soaking a fox canine and incisor in nitric acid (to remove the calcium) and cutting it into thin, 30 micron (i.e. about 330 slices to a centimetre or 847 to an inch), sections before staining it with a dye called Mayers Haemalun. The biologists established that the dark zones (incremental bands) were laid down during the autumn and winter and that, despite some problems discerning the bands (this apparently requires practice), the method offered “valuable possibilities for absolute age determination of Danish foxes”. In 1974, game biologist Stephen Allen used a slightly modified version of this technique to accurately age (i.e. correct to the nearest year) 95 foxes tagged as cubs in North Dakota and, in a 1993 paper to Gibier Faune Sauvage, Game Conservancy biologists H.N. Goddard and Jonathan Reynolds found that this method correctly aged six (66%) out of nine foxes of known age, was correct or over-estimated the age of 21 (91%) out of 23 foxes of known minimum age, and was one year below the known age in two animals. Goddard and Reynolds also found that the first dark line was deposited between January and March of the cub’s first year and suggested that both sexes are likely to be metabolically stressed during this period because, not only is this generally the coldest time of year, but it is also the breeding season.

More recently, Paul Simoens and colleagues at Ghent University in Belgium observed a good correlation between the age of a fox and the number of cementum growth rings; they found that domestic dogs were less accurately aged by this method and speculate this is because they no longer experience the seasonality that foxes are exposed to. Writing in a 2005 paper to Vlaams Diergeneeskundig Tijdschrift, Simoens and his colleagues raise an interesting question:

It may be wondered whether the gradual urbanization of red foxes will influence their natural way of life in such a manner that the cementum growth line count will no longer be reliable for age determination in these animals.

So, sectioning and staining a tooth seems to be the most reliable way of estimating the age of a dead fox, while the degree of wear of the incisors can give a fairly accurate estimate of live animals. Some authors have suggested that canine teeth are best to section, while others have found better results with incisors – in a recent (2007) paper to Folia Zoologica, however, Czech biologists Jana Roulichova and Milos Andera report that, although canines are best for the task, age can be estimated from any of the premolars. Whichever tooth type is chosen, it is often advisable to take multiple samples from the same animal. Harris, in his 1978 paper, found that:

For an accurate assessment of an animal’s age it is important to section more than one tooth because different teeth from the same animal may yield slightly different counts ... and so the determined age should be based on sections of at least two teeth.

Perhaps unsurprisingly, the longevity record for a Red fox comes from captivity. In his 2005 compendium, Longevity of Mammals in Captivity, Richard Weigl lists the oldest Red fox on record as being a mountain subspecies (Vulpes vulpes macroura) caught, in Utah, that arrived at Zoo Boise in Idaho during August 1985 at an estimated age of two years and four months; it was still alive in July 2004, when records were collected for the book, making it just over 21 years old. Zoo Boise’s registrar, Corinne Shaw, tells me that this vixen survived until January 2007, when she was euthanized by the vet because of age-related illness; she was thus estimated to have died at the age of 23 years and seven months. The oldest recorded European animal (listed as Vulpes vulpes crucigera) was a specimen that arrived at Giardino Zoologico di Roma in Italy during March 1980 – estimated at two years old -- and died there in January 1997, just shy of its 19th birthday. These longevities do, however, seem exceptional, and 14 is commonly cited as the upper age for captive foxes. Based on tooth-wear and cementum rings, a 15-year-old wild female fox has been recorded in Hokkaido (Japan) and a 13-year-old animal reported from Switzerland. There are also several records of animals attaining 10 or 11 years old, again based on tooth wear. The oldest confirmed wild fox I have come across is a female ear-tagged as a cub in April 1981 by Jaap Mulder and his team on the North-Holland Dune Reserve in The Netherlands; the animal was killed by a police officer in April 1993 at the age of 12 years. In a brief paper to Canadian Field Naturalist, Tony Chubbs and Frank Phillips reported on a male fox trapped during November 1994 in Goose Bay, Labrador aged 10 years and eight months. In his book, Running with the Fox, David Macdonald noted that the oldest wild fox he knew died ‘naturally’ at nine years old, while a reader in Colorado (USA) informs me that one of her resident males lived to 12 years old and a vixen still visiting her garden (whom she has known and photographed from a cub) is going strong at 12 years old.

Most wild foxes do not, however, live to anywhere near the aforementioned ages; between two and six years is typical. David Macdonald noted that only about 5% of foxes live past their fourth birthday and, in Oxford city, he and Patrick Doncaster found that 63% died during their first year; the average life expectancy was estimated at 19 months (only about 12% saw their second birthday). In Macdonald’s undisturbed/un-persecuted study group on Boar Hill in Oxford life expectancy was higher, with 23% living to five years old. Similar figures have been presented for foxes living in other cities. The average life expectancy can also be associated with dominance and Phil Baker at Bristol University found fox longevity to be related to social status, calculating that the average age for a dominant fox was about 4.5 years, while subordinates only lived for an average of just over two years. (Back to Menu)

Fox Broken LegMortality and Disability: Mortality rate varies considerably according to a host of factors, including age class, region, season, habitat, food availability and population density. Over large parts of their range, foxes are also persecuted by humans as a result of the damage they do (and their potential to do damage) to livestock. There are laws in place that regulate how a fox can be killed in Britain (i.e. it cannot, for example, be poisoned or gassed) but there is no law against killing this species and anybody with the appropriate licence and (depending on location) permission can do so at any time of the year (i.e. there’s no closed season). Consequently, it is impossible to obtain absolute values for the number of foxes killed in the UK each year. There are, however, some estimates available.

In their 2005 paper to the journal Animal Welfare, Bristol University biologists Stephen Harris and Phil Baker estimate that about 80,000 foxes are shot each year; roughly half by gamekeepers. In the Game Conservancy Trust’s 2000 report, Fox Control in the Countryside, Jonathan Reynolds notes that, of the foxes killed by Britain’s gamekeepers each year, about 30% are taken by ‘lamping’ (i.e. night-shooting with a high-powered, centre-fire rifle and spotlight), while 25% are caught in snares and a further 25% culled at cubbing earths (apparently 80% of foxes killed here are female); a further 10% are killed by terriers. I suspect these ratios have changed since the introduction of the Hunting Act (2004), which made it illegal to hunt foxes with a pack of hounds – a greater proportion of foxes are now likely to be shot. Regardless of the method of control, it is clear that a large number of foxes are born each year and a large number die. Indeed, the Bristol University team have calculated that Britain’s fox population swells to an estimated 675,000 individuals in late-spring, only to have dropped back down to around 258,000 individuals by the time the breeding season commences in the winter. In other words, some 425,000 cubs are born each year and a similar number of foxes (a mix of adults and cubs) die. In Britain an unknown number of foxes are killed by predators (see Predators) and disease (see Parasites and Diseases) each year, while an estimated 100,000 are killed by vehicles; during his studies in Oxford city, David Macdonald found that 60% of foxes were run-over. Indeed, the Bristol biologists suggest that road traffic collisions are probably the single biggest cause of fox mortality in this country, with such collisions more prevalent in urban than rural areas. In Bristol, three-month and seven-month old animals are apparently most susceptible to traffic collisions and this is associated with an increase in the cub’s ranging behaviour around the den site at these ages. In the recent Channel 4 documentary series, Foxes Live, it was estimated that pest controllers kill about 10,000 foxes in urban areas every year, although to the best of my knowledge there are no formal figures. (Image: X-ray of the front paws of a fox cub taken to Farplace Wildlife Rescue in County Durham. The cub's left leg is broken just above the ankle; such injuries, which can be caused by getting caught in fences, losing footing, etc., are not unusual among cubs.)

The mortality among cubs is typically high and may exceed that of adults. In their summary of urban foxes published in 2010, Carl Soulsbury and his colleagues gave annual mortality rates for juveniles in urban areas of 54-57% (Bristol), 64-66% (London) and 66-68% (Illinois), with comparable figures for adults of 50%, 53-56% and 61-74%, respectively. Elsewhere, the Bristol biologists have estimated that some 20% of cubs die underground (i.e. before about six weeks old), most as a result of fights with litter-mates as the social hierarchy becomes established. Indeed, a study on the cub mortality in Bristol found that 15% of four-week-old cubs died, of 1000 cubs born, 650 (65%) survived to sub-adult status and only 390 (39%) made it to adulthood. In Northern Ireland, during the mid-to-late 1960s, James Fairley found that 60-75% of cubs died in their first year while, in Russia, Nikolai Korytin found that 52% of cubs survived to six-months old, about 33% of juveniles made it to adulthood and 44% of adults died each year; cub survival in Russia was impacted more by extra-population factors (e.g. food availability) than by internal factors (e.g. density). Overall, in their 2004 review of the Red fox in Canids: Foxes, Wolves, Jackals and Dogs, David Macdonald and Jonathan Reynolds note that, globally:

“… roughly 75% of foxes die in their first year, and thereafter mortality is approximately 50% in each adult year.

Some specific causes of fox mortality are discussed separately elsewhere (i.e. Parasites and Diseases and Predators), but there are many other sources. Death by misadventure is a well known source of mortality, especially among cubs. Indeed, the aforementioned Bristol University study on cub survival found that some died when they became entangled in netting and washing lines or fell into ponds and swimming pools; other major sources of mortality included hypothermia, attack by domestic dogs, attack by badgers, and the death of the vixen. Foxes will scavenge and are consequently exposed to the associated risks, with at least one well-known case of large-scale secondary poisoning (i.e. caused by eating poisoned animals). The substantial die-off of foxes, pigeons and pheasants in Peterborough during November 1959 (and more widespread cases from across England until May 1960) were attributed to poison. In a relatively small arable area of eastern England alone, some 1,300 foxes died over a five month period. Several foxes were seen staggering around in broad daylight apparently blind (one vixen in Essex ‘blundered into’ a gamekeeper and another was found wandering around the Master of the Heythrop hounds’ yard); most were, nonetheless, in good body condition, suggesting they weren’t starving. Thorough investigation by a team at the Canine Health Centre (part of the Animal Health Trust) in Suffolk established that the foxes had died through indirect poisoning. Corn in the affected regions was being sprayed with chlorinated hydrocarbon insecticides (chemicals used to kill crop-eating insect pests) and the local birds were being killed when they ate the corn; the foxes had died after scavenging the poisoned birds. Similarly, a study in Europe between 1963 and 1971 found that 20 of the 32 foxes tested for thallium poisoning had sufficient quantities in their system for it to have been the cause of their death; thallium was commonly used in rodent poisons. More recently, of 34 foxes submitted to the Toxicology Laboratory of the Veterinary School in Lyon, France between 1991 and 1994, 31 had been poisoned by rodenticides, with high levels of the rodent poison bromadiolone in their livers. Foxes may also accumulate heavy metals and various toxic chemicals (e.g. PCBs, pesticides, etc.) and a study of 192 foxes collected from the Swiss city of Zurich and its suburbs during 1999 and 2000 found PCBs in the fatty tissues of all animals along with various pesticides; 70% tested positive for diealdrin, while 34% contained traces of DDT. The study, published in Environmental Health Perspectives during 2003, also found no significant difference between the levels of thesse compounds in urban and rural foxes, although they did establish higher concentrations in juveniles than in adults; the authors suggest that these fat-soluable compounds may be passed to cubs in the vixen's milk (indeed, adult females had lower PCB levels than adult males, supporting this theory). Concentrations of heavy metals (e.g. cadmium, lead, copper, zinc, etc.) appear to vary according to habitat and a 2001 study by Swiss biologists found that urban foxes had higher lead, but lower cadmium, concentrations in their liver and kidney tissues than surrounding suburban and rural animals. The accumulation of cadmium was considered to be picked up from the soil by invertebrates (esp. earthworms) and plants (fruit) and transferred to suburban and rural animals that are eating more wild food; urban animals were less affected because their diet contained large quantities of human food, which is only permitted for consumption if cadmium is below trace levels. Lead was presumably accumulated from industrial outputs (e.g. manufacturing), explaining the higher concentrations in urban environments. What impact these chemicals have on the foxes are unknown, but in humans and other species they have been linked with cancers, neurological diseases and reproductive failure.

Foxes may occasionally fall foul of other foxes and both infanticide (killing of young) and cannibalism are known in this species (see Q/A). Fights between foxes over territory or access to mates are common and can be serious. Indeed, the popular literature is replete with descriptions of fights between foxes, often involving the stereotypical ‘fox trotting’ behaviour where the two animals rear up on their hind legs and attempt to push each other over (See: Behaviour and Sociality). In most cases, these fights are fast, aggressive and noisy, but generally do little permanent damage. In some -- apparently quite rare -- cases, however, such disputes can prove fatal. In a 1987 paper to the Journal of Applied Ecology, Stephen Harris and Gerald Smith report that fights with other foxes accounted for about 3% of the deaths in a low-density population in Bristol; unsurprisingly, this rose to 7% in a nearby high-density population. Harris and Smith also note that adult fox mortality increased during the breeding season, when they’re more mobile and more likely to encroach on another animal’s territory. Similarly, in a short paper to the Veterinary Record during 1995, M.A.F.F. biologists Paul Duff and B. Hunt report that, of 27 foxes autopsied between 1989 and 1994, seven (26%) adult deaths were associated with deep bite wounds believed to have been inflicted by other foxes and all occurred between January and February (the breeding season); most casualties were males and bite wounds tended to be focused around the face and back of the neck). In one particular vixen, Duff and Hunt found evidence of a particularly serious attack, with multiple bite wounds and skin lacerations.

Fox fights are frequently heard, but rarely seen. Occasionally, however, the attack is captured on film. One such incident occurred during April 2005 in Chertsey, Surrey between midnight and 5:30am. The following is an extract of an e-mail I received from a reader describing the incident that took place in his driveway (reproduced with his permission):

We went to take the children to school and when we stepped out of the front door, the car was surrounded on three sides by blood on the beige block we had recently had put down. The car too had lots of blood on the lower door sills and beneath the front grill and bumper where something had been dragged or carried bleeding around the car. The trail continued around the drive and car to the front "walk through" gate and then disappeared along the public footpath.

It seems that there were certainly 3 foxes but possibly a 4th involved over about a 2 hour period of much activity in the drive, the bushes, and around the car and down the side of the house to the side gate. The activity was at times fierce and prolonged attacks between 3 foxes, culminating in a fox being dragged by the neck along the drive from the side of the house around three sides of our car before disappearing out of the gate to the public footpath. After the event, another fox or one of the same original ones called to look around the drive and car, very cautiously in case he was on someone else’s territory.

This encounter was captured on the gentleman’s home security CCTV camera and certainly sounds like a territorial takeover. How often such usurping occurs and what happens to the territory holders afterwards is unknown and warrants further study.

Fox Fight
Violent physical contact between foxes can sometimes result in the injury or death of one or both parties, although such fighting is rare; instead foxes use a suite of behaviours (largely in the form of body postures and calls) to establish dominance, with a goal to avoid fighting and thus the potential injury it brings. In many cases, fighting can be mistaken for play when captured in photographs, although the body language of the fox can be used to decipher the meaning of the interaction. This image is one of a series captured by amateur photographer and naturalist Philip Jones and shows two foxes meeting, presumably at the boundary of a territory. The animal on the left has adopted a dominant stance, while the one on the right is clearly submissive. The result was the submissive animal being chased out of the field.

It is worth mentioning that not all foxes shot or hit by cars are killed. There seems to be a popular opinion that many wounded foxes crawl away somewhere and die of gangrene – this is an argument I have heard many times from people who consider hunting with hounds a more humane form of fox control than shooting. Former M.A.F.F. biologist Huw Gwyn Lloyd disputed this suggestion in his 1980 book The Red Fox, in which he described various examples of foxes he’d autopsied and found bullets (or bullet fragments) lodged in various organs -- including the heart -- but that had not caused death. Lloyd also noted various other healed wounds, including broken limb bones, loss of one-or-more feet and, in one vixen, a broken fox snare entirely embedded in the healed skin around her loins and, despite this impairment, she was apparently in good health. Lloyd concluded that:

Whilst the fox with a heavy load of shot may die, especially if shot in the viscera, the assumption that gangrene will set in is fallacious.”

Lloyd’s findings are in line with those of Bristol University’s Stephen Harris who, in a 1978 paper to the Journal of Zoology, described the injuries to 331 foxes living in suburban London. Harris found that 30% of females and 35% of males had at least one healed fracture; when the dataset was rearranged to look at what impact age had, Harris found that older foxes had significantly more fractures than younger ones, with 70% of foxes over five years old having at least one fracture, compared to just under 30% of two and three-year-olds. The majority (almost 60%) of the fractures that Harris documented were in the hind quarters, although broken ribs were also relatively common. Harris noted lead pellets lodged in the healed bones of two animals, air rifle pellets in two others, one animal with two 0.22 air rifle pellets embedded in its left eye-socket and an animal with an arrow projecting from its chest. It seems that these injuries caused the foxes little problem, although it is known that they can accentuate the development of arthritis in later life and this condition is relatively well known in older animals – in an earlier study, Harris found 86 (34.5%) of the 252 adult fox skeletons from London he studied had spinal arthritis, with occurrence increasing with age class (14% of one year olds to 90% of five years or older). Working in Sweden, Jan Englund studied the skull and leg bones of several thousand foxes and found that up to 40% of animals three years or older had survived some shooting accident. A most remarkable account of recovery from an apparent gunshot was given by the late Eric Ashby in his superb 2000 book, My Life with Foxes, in which he wrote:

One feeder of wild foxes has told us that one of her regular visitors arrived one evening with her head covered in blood. The fox had a large hole on one side of its skull and a smaller one exactly opposite, almost certainly the result of a bullet passing right through. It was even possible to see daylight from one hole through to the other. A few weeks later, without the help of a vet and despite the difficulties of continuing to survive in the wild, the wound had healed completely and could barely be seen.

Ultimately, the findings of Lloyd, Harris, Englund and Ashby suggest that foxes heal remarkably quickly.

Some of the ‘milder’ conditions affecting this species include various bone disorders. Syndactyly -- the fusing of the toes -- has been described in foxes and Harris found one vixen with what could only be described as ‘webbed feet’. Osteomalacia also sometimes occurs; this is a generalized bone condition resulting in a softening (or reduced density) of bones, leading to deformity because they cannot support the forces applied to them. In The Red Fox, Lloyd notes that rickets (lack of Vitamin D) is occasionally found in fox cubs and quite common in captive animals; he suggests that the skin of prey probably provides wild animals with more than enough vitamin D.

Several authors have recorded dental anomalies in foxes; typically missing teeth. In 1965 Elmer Birney, at Fort Hays Kansas State College Zoology Department, described a male Red fox skull missing three teeth (one pre-molar and two molars) from the lower jaw, while a Danish study published in 1940 reported that 11 (8%) of their fox skulls had some form of aberrant dentition, although only four animals were missing so many teeth. In some cases additional teeth can grow in the jaw, they can be smaller than normal, have different root shapes, be impacted, etc. Indeed, in a paper to the journal Acta Theriologica during 2008, Martina Nentvichová and Miloš Anděra reported dental anomalies in 170 (22%) of the 785 Czech Red fox skulls they examined. Generally speaking, such dental anomalies don’t seem to detrimentally impact the animal’s survival. Some disabilities may, however, be more debilitating. In Oxford, the WildCRU team tracked a one-eyed vixen that successfully raised two litters of cubs; she later developed a cataract in her working eye and was subsequently hit by a car and killed. A male fox, nick-named Oedipus by Oxford’s Patrick Doncaster, went blind during the study and -- despite getting entangled in netting and shrubs and walking into trees, Dr Doncaster’s legs and even another fox -- seemed to have little trouble finding food and lived for just over two years. This does raise the, as yet un-answered, question of whether urban environments permit the survival of foxes that would perish in the countryside.

Before leaving the subject of mortality, it is worth briefly mentioning population recovery rates. The question of what controls fox populations and how they respond to culling has been dealt with elsewhere (see Q/A), so I won’t go into any detail here. Suffice to say, fox populations have impressive potential to recover from heavy losses. In a fascinating paper to the German veterinary journal Zentralblatt fur Veterinarmedizin, a team of World Health Organization vets led by Konrad Bogel modelled how fox populations respond to various levels of culling associated with rabies control. Bogel and his team considered that a population increase of up to about 70% in a single year was possible (i.e. the population can replace 70% of individuals within a year), although most populations would recover more slowly. The researchers estimated that recovery from 25%, 40% and 60% levels (i.e. the population drops by 75%, 60% and 40%) would take place within four, three and two years, respectively. Essentially, a population that’s reduced to 40-50% of their original level can recover within three years, in the absence of further culling. These are, of course, estimates based on mathematical models and unpredictable factors, such as food availability and climate can have a substantial impact on the speed of recovery. Field observations suggest that, although more vixens breed in low density populations, it is primarily increased survival that drives the recovery. (Back to Menu)

Red fox with MangeParasites and Diseases: Foxes are known to harbour a range of different parasites, both internally and externally, including various species of intestinal worms, flukes, lungworm, heartworm, ticks, mites, fleas, protozoans, bacteria and fungi. Some of those of greatest concern, owing to them being zoonoses (i.e. can be transferred to humans), include Toxocara canis (dog roundworm), Echinococcus multilocularis (hyatid worm) and Trichinella spiralis (muscle worm). Toxocara is present in the UK, although foxes don’t appear to be a significant link in the ‘infection chain’. Echinococcus is currently considered by DEFRA to be absent from Britain, while the last confirmed case of Trichinella in a fox from Britain was in 1957. Angiostrongylus vasorum (canine heartworm) and Sarcoptes scabiei (mange mite) are also important parasites of foxes that can be passed to domestic dogs. In Britain, the average prevalence of the heartworm is 7% (although locally prevalence can reach almost 30%) and it is widely considered that slugs and snails are a more significant source of infection than foxes. Mange (image, right) can be a significant problem and cause large-scale declines in the fox population; the mites can be transferred to domestic dogs, but infection is easily treated.

Wounded foxes can be susceptible to secondary bacterial infections (notably with Streptococcus) and myiasis (a condition, also known as fly-strike or blowfly, where parasitic flies lay eggs in open wounds and the newly-hatched larvae feed on the tissue), although there is little evidence of gangrene in this species. Possibly the pathogen of greatest concern is rabies, for which the Red fox is the major sylvatic vector (wildlife carrier) in Europe. The virus is transferred through a bite and can be fatal to both humans and other animals (including foxes); large scale vaccination of foxes has served to control the spread of rabies in recent years, eradicating it altogether from parts of western Europe. Foxes are also capable of carrying bovine tuberculosis (although apparently aren’t infectious) and Weil’s disease, although they aren’t considered significant vectors for either disease. Recent work by biologists at the Royal Veterinary College in London isolated Staphylococcus aureus bacteria, although they didn't find any Methicillin-resistant S. aureus (MRSA). Mange, rabies and fox parasites in general are covered in more detail in the associated Q/A.

Some of the most endearing stories of fox cunning revolve around how they remove parasites; most notably how they rid themselves of fleas and lice. Legend has it that foxes rid themselves of lice and/or fleas by holding some wool, or corn silk, grass, bark, etc. in their mouth and walking backwards into water; this causes the fleas to move up the fox’s body and onto the object in the mouth, to escape drowning, which the fox then releases, and off it floats with all the fleas. The author Ernest Seton apparently witnessed this behaviour -- he wrote about it in 1929 -- and then analysed the wad of corn silk that the fox had evidently been holding; on it he apparently found lice. Lloyd, in his book The Red Fox, mentions that Alex Wetmore recorded a similar behaviour by a Grey fox (Urocyon cinereoargenteus) in a 1952 article to the Journal of Mammalogy; curiously, I can see no sign of this in the paper (it’s entirely about the attraction of a grey fox to a crow call and decoys). Regardless, Lloyd, like many others, had his doubts as to the validity of such accounts:

The practical objection to the story is that the skin of the fox would not become wet through by this rather gradual immersion, so the fleas would not be in any danger of drowning…”

Despite the improbability of such behaviour, it’s an interesting story that has persisted since at least Hellenic times, around 323 BC.

Pair of Red foxesSexing: The question of how to tell the sex of a fox in the field is one frequently asked, but to which there isn’t a straight answer. Over the years, many authors have professed sure-fire methods for telling vixens (females) from dogs (males), but in practice there is very little sexual dimorphism in Red foxes (i.e. the males and females look very similar). Some proposed methods of separation, the origins of which are lost in antiquity, have since been proven untrue. A white tip on the tail isn’t, for example, indicative of either sex – this ‘brush tag’ can be present in both dogs and vixen, or may be absent altogether. Similarly, a proportionally shorter coat and squatting while urinating are often, but not exclusively, associated with vixens. In his 1906 Foxes at Home, Colonel Talbot described how vixens carry their heads higher than dogs, have thinner necks and hold their brushes differently. Subsequent authors, Roger Burrows for example, have failed to notice any significant differences in those features. Burrows also mentioned how some hunters claim to be able to sex a fox based on close study of its paw print (that of a vixen being smaller than that of a dog), but pointed out that this was not something he could ever do. Brian Vezey-Fitzgerald, in his 1968 Town Fox, Country Fox, provided several intimations given by others on how best to sex a fox in the field, adding to the aforementioned suggestions that there is apparently a belief among country folk that golden cubs are always vixens. Fur colour is not sexually dimorphic in foxes and, as such, golden cubs can be of either sex. Size is sometimes used to infer sex, insomuch as dogs tend to be larger and (approx. 17%) heavier than vixens, as are the type of calls each sex make; these are, however, generally unreliable indicators of sex. Vezey-Fitzgerald came to the conclusion that some naturalists still hold today:

I remain firmly of the opinion that you cannot tell dog-fox from vixen at sight in the field with any certainty.

There are, nonetheless, a couple of fairly accurate methods of telling vixens and dogs apart in the field, although one requires some experience. The first, and by far the most straightforward, is to look for the cream-coloured fur of the scrotum (which identifies a male) or the teats of a lactating female; these features are, however, not always apparent, being prominent only during certain seasons. The second method involves looking at the face of the animal; more specifically, the breadth of the head and the position of the ears relative to the nose. In 1962, the eminent naturalist and fox farmer Henry George Hurrell noted that males generally have broader heads and thicker muzzles than females and, in 1968, Burrows described how this broadness causes the ears of a dog fox to form a ‘W’-shape when viewed head-on, whereas they form a ‘V’ in vixens. Indeed, the heads of vixens are generally more triangular in shape. Several authors have apparently used these features to successfully sex foxes in the wild and Stephen Harris included it in a brief article to the May 2007 issue of BBC Wildlife Magazine, although in The Red Fox, Lloyd cautioned:

There certainly is such a difference, but it is not often easy to distinguish the sexes in isolation.

If you happen to be examining the skull of a fox, and have a pair of callipers to hand, taking some measurements and applying them to a simple calculation allows for the separation of vixens and dogs in 70% to 90% of cases. Early work on farmed and wild foxes by Canadian researcher Charles Churcher revealed that taking three measurements of the skull (the total length, zygomatic width and mastoid width – see diagram) allowed the correct sexing of 101 of 113 specimens (i.e. was about 90% accurate). Churcher looked at various measurements of the skull and found that he couldn’t accurately separate males from females based on a ridge of bone that runs along the top of the skull called the sagittal crest. Nonetheless, subsequent authors have since found this feature to be of considerable use and, in their contribution to the fourth (2008) edition of Mammals of the British Isles, Stephen Harris and Phil Baker note that, in animals 10 months and older, males can be separated from females by the sagittal crest with an accuracy of 70%. Harris and Baker do note, however, that the crest is poorly developed or absent in males younger than 10 months, causing their skulls to look like those of vixens. This is a finding echoed by many naturalists, who note that young males have faces more similar to vixens; the skull broadening with increasing age.

In a 1980 paper to the Journal of Zoology, M.A.F.F. biologists L.W. Huson and Robert Page noted similar age-related variation; they found that male skulls changed more with age than those of vixens. More recently, a team of Czech researchers found that, in both sexes, the skulls grow rapidly in length during the first six months of life, reaching full length at around this age; the skull then continues to grow in width. The researchers also noted some differences between the sexes: in males the jugular breadth, for example, increases after six months old, while in the female it does not. Consequently, sexual dimorphism was evident in skulls at the age six-and-a-half months to one year old.

In an earlier paper to the same journal, Huson and Page were able to correctly sex 80% of the 192 skulls they collected from south-east England using only two measurements (total length and palatal length) and, by adding two more measurements (zygomatic width and condylo-basal length) they were able to correctly sex 88% of 379 Welsh fox skulls. Similar success was achieved by John Lynch working in north-east Ireland during 1996. In his study of 204 adult Red fox skulls held at the Ulster Museum in Belfast, Lynch found that dog skulls were larger, longer and had a narrower post-orbital constriction than vixen skulls; based on these characters, he was able to correctly sex 87% of his skulls. Lynch considered that the narrower inter-orbital constriction could permit the dog fox a greater bite force and therefore allow it to handle relatively larger prey. If you’re interested in the calculation Lynch presented click here. The Czech research mentioned earlier found similar results to those reported by Lynch and, in a 2010 paper to Folia Zoologica; they noted that male skulls were significantly larger than those of females in all measurements they took except one: the postorbital breadth, which was wider in females than males. The anatomists wrote:

The narrower postorbital constriction and a longer and higher sagittal crest enlarge the area for muscle insertion and the male jaw becomes stronger.

In other words, having this narrower area of bone just behind the eye sockets leaves more room to anchor a large masseter (chewing) muscle, thereby potentially allowing the fox to take relatively larger prey. The suggestion is that this may allow for some niche separation between the sexes (i.e. males taking larger prey items than females), but there is currently no evidence that this has happened.

Finally, it is not just skull measurements that can be used to separate the sexes. In a 2008 paper Elwira Szuma looked at the teeth of just under 3,000 Red foxes collected from across the Northern Hemisphere and found that those of males and females differed from one another, most notably the canines and carnassials; overall, male canines were 3.6% larger than those of females. Szuma also found that there was more of a difference between the sexes in the Palaearctic (Europe and Asia) than in the Nearctic (North American) foxes. (Back to Menu)

Red fox pair
A pair of Red foxes on the Isle of Wight. Here you can see a dog fox on the left and a vixen on the right - note the dog's broader head compared with the v-shaped vixen.

Activity: From the outset it must be noted that it is incredibly difficult to generalise about the behaviour of any animal – there will always be exceptions to the ‘rules’. This seems particularly true of fox activity, which varies according to a whole host of factors, including the individual, sex, age, season, habitat, and weather. Indeed, one study of Japanese foxes, published in the Japanese Journal of Ecology during 1980, noted how:

Day to day variations are rather common and large even for the same individual.

Foxes are active throughout the year and do not hibernate. They’re predominantly nocturnal, with a tendency towards crepuscularity (i.e. peaks of activity around dusk and dawn) and, although diurnal (daytime) activity is common in some areas, foxes typically spend the day resting in cover. Indeed, during a 1986 study of fox activity in central Spain, Juan Carlos Blanco found that foxes rarely moved far during the daytime: of 176 radio-fixes of a dog fox between 2.5 hours after sunrise to sunset, 95% showed it to be inactive. That said, in certain regions -- most notably urban areas -- diurnal activity is more common than many people realise. People often seem surprised to come across a fox out-and-about in broad daylight, but I have watched foxes hunt during the late morning in rural locations, take one of our ducks at lunchtime on a weekday, and stroll around a busy industrial site in the middle of the afternoon; one even invaded the Twickenham rugby pitch at 14:55 on 13th March 2011 in front of 82,000 fans just before England played Wales in the Six Nations. It has been suggested that the level of diurnal activity among foxes is associated with the level of persecution and, in his 1950 book Wild Animals in Britain, Oliver Pike wrote:

The fox is now a nocturnal hunter; but this is probably a habit forced upon it by continual persecution. The foxes that lived in Britain in the long distant past searched for their food by day, and we often see them falling back to this habit [where there is little or no persecution].”

I suspect that there is more to the fox’s penchant for nocturnality than human disturbance but persecution does, nonetheless, have a role to play. Studies on several mammal species -- including European badgers (Meles meles), Coyotes (Canis latrans), and Bat-eared foxes (Otocyon megalotis) -- have shown that persecution by humans causes the animals to become more nocturnal, sometimes reverting back to more daytime activity if the persecution is stopped. My own observations suggest that something similar operates among Red foxes – I’ve found that foxes are considerably more difficult to find during the daytime in rural areas where they are heavily controlled by farmers or gamekeepers and there are some tracking data suggesting that human activity has an impact on the nocturnal behaviour of Red foxes. Biologists working in Japan’s Kumamoto Prefecture during the 1970s, for example, found that one of their study animals had conspicuous nocturnal activity throughout the year. This dog fox had a territory encompassing many villages and roads carrying heavy traffic and the researchers observed that human disturbance triggered many daytime movements of the foxes; being driven away from resting sites by farm workers and, in one case, chased by a pack of feral dogs. In their 1980 paper, the authors concluded that: “frequent passages of men and motor-cars suppresses the activity of the fox.”  Similarly, a study of foxes in Italy’s Maremma Natural Park found that the animals used areas under human management mainly at night, with almost 86% of their activity being nocturnal.

Red fox patrollingVarious tracking studies have revealed that the bulk of a fox’s activity occurs during the night, with most activity starting just after sunset and ceasing in the hour prior to sunrise. On longer autumn and winter nights, it seems that the fox has more time to complete its business and, consequently, there is often a period of rest (ranging from about 20 minutes to three hours) around midnight during these seasons; most studies have shown either bimodal or trimodal activity cycles (i.e. two or three peaks in activity per night). Both juveniles and adults show increased levels of activity during the autumn; the former often travelling further on exploratory trips prior to dispersal and the latter feeding up in preparation for the breeding season. During the winter, adults are very active as they move around in search of mates – males will often undertake considerable movements outside of their territory looking for receptive vixens.

During his studies on captive foxes in the 1950s, German ethologist Günter Tembrock recorded an activity peak of 12 hours per day during pre- and early-breeding season, dropping to seven hours per day in April and remaining there for the remainder of the year. During autumn and winter Tembrock noted little daytime activity but found a large peak in activity at dusk, falling during the night towards dawn. Tembrock observed that activity was more evenly spread throughout 24 hours between February and March, after which daytime activity reduced and nocturnal activity occurred in three peaks, punctuated by brief periods of rest. During his studies on foxes in west Gloucestershire, Roger Burrows found something similar; he noted how activity was spread over the whole 24 hour period during January, with movement apparently being more important than feeding at this time. Burrows did, nonetheless, document more daytime activity during December (nocturnal movements being more sporadic) and observed less daytime activity during February (most activity being between about 6pm and 8am), increasing during March and April. Burrows also noted that foxes took more direct routes (across the middle of open fields that they skirted the edge of during winter) more often during May, which he considered was probably a response to higher vegetation providing better cover. A recent study by researchers at Brighton University tracked a male fox 315 km (195 miles) in almost a month (early December 2013 to early January 2014) and observed that most of this travelling was done at night, with the fox slowing down between 5am and 6am to look for somewhere (generally a suburban garden) to rest up for the day. This former suburban dog fox appeared to navigate along roads and railway lines, occasionally swimming across rivers having walked up and down the bank looking for a good place to cross.

During the early 1980s, much was learnt about the activity patterns and movements of urban foxes in Britain. Between October 1980 and January 1983, Oxford University zoologists Patrick Doncaster and David Macdonald radio-tracked 17 adult foxes living in Oxford city; the results of the study were published in the Journal of Zoology during 1997. The biologists found that the foxes were largely inactive by day (and often rested during part of the night) and, for all foxes, the first prolonged activity began, on average, 30 minutes after sunset and ended 15 minutes before dawn – the day of the week wasn’t found to alter the activity pattern. The average time spent active (when lactating vixens were excluded – see below) was just under seven hours per night, with no noticeable difference between dogs and vixens. The overall time spent active per night didn’t change seasonally. Where the foxes chose to go on any given night was loosely dependent on where they had been the previous night, although they generally used less than half of their home range on any one night. Overall, the researchers found that the number of resting periods increased as winter approached; during winter and spring the night was typically divided into several short periods of activity (2 – 2.5 hours each) interspersed with similar periods of rest. These rest periods are longer and activity periods shorter than those recorded in more rural habitats (22 – 29 minutes of rest and 10 hours of activity among foxes of the Jura Mountains in Switzerland, for example), but very similar to those recorded in Bristol’s urban foxes (active for about eight hours per night). Doncaster and Macdonald suggest that this difference is related to food: urban foxes live in a food-rich habitat, with clumped resources, meaning they don’t need to search as far or for as long to find sufficient food as foxes in mountainous regions.

The length of time taken to find food is not the only factor that influences activity – the activity of the prey can also be a factor. During their study on foxes in Tuscany, central Italy, Paolo Cavallini and Sandro Lovari found that foxes were more diurnal when feeding on diurnal grasshoppers. In other words, how active the foxes were during daylight depended on how much of their food was active during the day.

The activity of breeding vixens is substantially reduced during March and early April and females with cubs are significantly less active than non-breeding animals. In the days leading up to parturition, the vixen will restrict herself to the earth and will not leave the cubs during the first 48 hours. Once the cubs are a couple of days old, the vixen will leave to drink and as the cubs grow the vixen’s activity away from the earth increases (she will move further away and stay away for longer). Not only are vixens less active while rearing cubs, they also travel shorter distances.    Indeed, a tracking study of foxes in the Ashio Mountains of central Japan, between November 1988 and September 1989, showed a vixen decreased her home range by almost 50% while she had dependent cubs, increasing it again once the cubs were above ground. The researchers continuously recorded the vixen’s activity for a 60 hour period during mid-April and found that she stayed in the den for more than 80% of the time, making only 14 trips out (only five of which exceeded an hour, most being only a few minutes). Unfortunately, this study only tracked a single vixen, so it is difficult to draw many conclusions, although several other studies have yielded similar results. In a study of foxes living in the Kumamoto Prefecture of Japan during the 1970s, Kazuhiro Eguchi and Toshiyuki Nakazono found that, although vixens nursing cubs were active both day and night, the total distance that they travelled during the day was short. Likewise, during their Oxford study, Doncaster and Macdonald found lactating vixens spent, on average, only four hours per night active and moving substantially shorter distances than non-lactating animals (although the authors don’t state precisely how far); non-lactating animals moved an average of 4.5 km (3 miles) per night, covering an area of almost 18 hectares (ca. one-14th sq. mile).

It’s not only adult foxes that undergo seasonal changes in their activity patterns – cubs do too. Indeed, in his 1994 book Wild Guide, Simon King notes that mid-to-late May is the best time for fox-watching because daytime activity of adults (with hungry cubs to feed) and cubs is at its peak. King describes how cubs become increasingly crepuscular/nocturnal (and more nervous of humans) by June or early July, an observation that Roger Burrows also made, in his Wild Fox book. Indeed, Burrows frequently observed cubs playing above ground during May, getting progressively more nocturnal (seldom out before dusk in June) as they began wandering around by themselves. A tracking study of fox cubs in Bristol between 1991 and 1993 revealed that cubs began using more lying-up sites away from the main earth from June onwards such that, as the summer progressed, the cubs became more scattered, spending less time at the earth, and were less likely to lay-up in groups. By August the cubs were more active around the territory, moving over areas of a similar size to that of their parents. Overall, between May and August the cubs increased the area over which they moved by seven-fold, with most activity centred around secure rendezvous sites located in dense vegetation. Cubs are active for roughly the same, or slightly longer, periods as their parents.

Essentially, how far the fox travels is determined by two main factors: season (which affects food availability and distribution along with breeding) and habitat (which also affects food as well as disturbance). Weather conditions can significantly influence the times a fox is active and, while tracking the foxes of Cedar Creek in Minnesota, Alan Sargeant found that they switched from nocturnal to diurnal feeding when snow cover was very thick (in some cases, exceeding 1m / 3ft).

Finally, much is made of the speed that foxes move around their territory. Doncaster and Macdonald found that their Oxford urban foxes travelled at, on average 0.6 kmph/0.4 mph (roughly 10m or 33ft per minute); a similar study in Bristol found that speed of movement varied considerably with habitat, but was as high as 2 kmph/1.2 mph. In their contribution to Mammals of the British Isles, Stephen Harris and Phil Baker note that, when moving un-hurriedly at a slow trot, foxes attain 6 – 13 kmph (4 – 8 mph), while considerably faster speeds have been reported for fleeing foxes. During their study of foxes in Kyushua (Japan), Eguchi and Nakazono observed the normal walking (trotting) speed to be about 7 kmph/4.4 mph, although they note that the average speed is much lower than this because the fox engages in various activities (prey searching, hunting, sniffing, etc.) while moving around. Burrows noted how, when in a hurry, a fox gallops along at up to 56 kmph (35 mph). In a 1968 paper to the journal Saugetierkunde Mitteilungen, German mammalogist Theodor Haltenorth and Italian FAO biologist H. Roth report a top speed of 48 km/h (30 mph) and a maximum vertical jumping height from standing of 2m (7ft) for Red foxes. Huw Lloyd, in his The Red Fox, noted something similar:

I am uncertain of the top speed of the fox. I have followed one along a road at just over 48km per hour, but it is commonly held that the fox is capable of over 65km per hour [40 mph].”

Red fox trotting

Harris and Baker, however, suggest that the oft-cited top speed of 65 kmph is probably unrealistic; it would certainly put the Red fox just shy of the top speed typically reported in greyhounds (45 mph, although one Australian dog apparently topped 84 mph!), although Gray foxes (Urocyon cinereoargenteus) have apparently been clocked at 42 mph (68 kmph). Either way, if similar speeds are attained by the Red fox, they are presumably short-lived. (Back to Menu)

Red fox at earthDens/Earths and Resting Sites: Foxes sometimes take up residence underground in excavations called earths or dens – these terms are used interchangeably, although earth tends to be a British term, while den is more commonly used in American and European literature. In some early, particularly hunting, literature an earth is occasionally referred to as a ‘kennel’ or ‘lair’. At its most simplistic, an earth is a hole dug into the ground, with a hollowed-out chamber at the end of the entrance tunnel in which the fox sleeps and in which cubs are raised. The chambers are typically between one and three metres (3–10 ft) below ground, with tunnels generally leading to more than one entrance (a main entrance and emergency exit); in his Walker’s Carnivores of the World, Ronald Nowak gives the largest number of entrances for a single earth as 19. The entrance tunnel is typically between five and seven metres (16–23 ft), although they may reach up to 17 m long (56 ft). According to Vladimir Heptner and Nikolai Naoumov, in their 1988 Mammals of the Soviet Union, foxes dig downwards at an angle of 40 to 45-degrees, creating tunnels 15 to 20 cm (8 in.) in height and 25 to 30 cm (12 in.) wide, depending on the soil type; entrances are oval or rounded, 30 to 40 cm (16 in.) wide and up to 70 cm (2 ft 4 in.) tall. In some instances there may be more than one earth within a territory: smaller ‘standard’ earths used for resting and a larger ‘natal’ earth in which the cubs are born and raised. A characteristic of earths is a lack of bedding (unlike badgers that periodically bring fresh vegetation back to the sett, foxes do not use bedding material); they may also mark the entrance with scat. An earth may be used for several consecutive years.

Suitable earths are an important resource for foxes and a recent survey in Germany concluded that the availability of suitable territories, containing convenient breeding dens, was a crucial factor limiting the country’s fox population. Consequently, foxes tend to be less ‘picky’ about the type of places they use as den sites than some other animals. A study published in the Southwestern Naturalist back in 2000 found that Swift fox (Vulpes velox) earths on the Great Plains of North America were pretty much identical with respect to size, number, direction and shape of openings, distance between openings, dimensions of tailings, slope of site, surface roughness and ruggedness of site, surrounding vegetation and soil type. This suggests that foxes seem to be capable of exploiting resources in most available habitats, although there are some features that foxes seem to look for when selecting an earth or potential earth site. Preferred den sites tend to be on sheltered (among trees, under buildings or under dense vegetation such as bramble), well-drained ground (often slopes) with loose, easily dug, soil. In a study of fox populations in Hakel, eastern Germany, Michael Stubbe found that 95% of the 145 earths he looked at were on south east-facing slopes, which had an average inclination of 20-30 degrees. Sometimes habitat preferences are also apparent and a study of foxes in Tuscany, Central Italy, found they showed a preference for marquis (scrubwood), meadows and pine forests in which to create earths, with the former being most (and latter least) used during cold seasons.

Foxes tend to tolerate more human disturbance than many other mammals. In a study of fox and badger dens in the Kampinos National Park, central Poland, botanist Przemyslaw Kurek found that foxes showed no particular preference for the placement of their earths, settling significantly closer to urban areas than badgers. Kurek suggested that there are two reasons behind this settlement pattern: in the first instance foxes lived at higher densities within the reserve than badgers, so they may not have the luxury of choice; secondly, foxes are generally much less “anthrophobic” (i.e. scared of people) than badgers. Consequently, foxes have little problem finding suitable den sites in our towns and cities. Urban foxes will readily make dens in all sorts of places. In their 2001 book Urban Foxes, Stephen Harris and Phil Baker describe various examples, including foxes raising cubs in the false ceiling of an architect’s office, under the kitchen floor of an occupied house (the adults were apparently frequently chased down the hallway by the family’s dog), and another similar example in which the foxes chewed through gas pipes causing a major gas leak. There are also various reports of foxes raising cubs under the floorboards of classrooms and in the 54,000-seater Yankee Stadium in New York. In his Running with the Fox, David Macdonald described how, in the late 1970s, a vixen burrowed into the earth mound above an underground chamber housing Oxford University’s seismograph, causing it to register a series of spurious earthquakes! As endearing as it may sound to some to have a littler of cubs under your floorboards, they can be a considerable nuisance. Harris and Baker describe the chewing of electrical cables, the noise made by cubs playing under the floor throughout the night; not to mention the smells, dust, etc.

While it is fairly common for foxes to raise cubs in disused (or rarely used) buildings, examples of them denning in occupied houses are rare. Ordinarily, urban foxes confine their activities to our gardens and arguably the most popular urban earth sites are under garden sheds. A study in Bristol city found 37% of earths were under sheds; other studies found around 15% in Oxford city and 25% in an area of London were similarly located. In Melbourne, Australia, Clive Marks and Tim Bloomfield found that 44% of earths were dug under buildings and out-houses, while a survey of foxes in Germany found about 12% of breeding dens were associated with buildings. Other locations in urban settings include earths dug into rockeries, earth banks (31% in Marks and Bloofield’s Melbourne fox population) including railway embankments, flowerbeds, under gravestones in cemeteries, and among tree roots. In fact, foxes don’t always stop at the base of the tree and people have been, justifiably, surprised to find foxes in trees. Unlike Gray foxes and cats, Red foxes don’t have much rotation in their forearms and so cannot climb trees in the same way (i.e. grasping both sides of the trunk and pushing up with their hind legs); this limits them to trees with low branches on to which they can jump, or with shallow-sloping trunks. Regardless, foxes will often climb trees to search for food (birds, eggs, fruit, etc.), escape flooding, or simply to rest in the sunshine, but in some rare cases they have been known to make arboreal dens. Indeed, in Urban Foxes Harris and Baker wrote:

"In one instance, in a cemetery in Bristol, an evergreen oak had been extensively pruned and shaped, and all the cut twigs and leaves had accumulated in the crown of the tree to form an impenetrable mass amongst the branches. The vixen had climbed into the tree and dug an extensive burrow system amongst the compacted prunings. Here she gave birth to her cubs for several years running, only moving them out of the tree once they were big enough to play."

Red fox earthRed fox earth
Fox earths/dens are often dug into earth banks or made under dense patches of bramble, hawthorn or gorse. Fox earths are distinguished from badger setts by the lack of bedding and the droppings and food remains often found in the vicinity. The area of the earth can look particulaly 'untidy' when cubs are present.

More recently, a family of four foxes made the British press when they made what appeared to be an earth, nine metres (30ft) up a tree in a back garden in Ipswich, Suffolk during January 2009. Generally speaking foxes making earths in trees is rare, although it is not uncommon for them to be found resting on branches during the day and, in his 1968 book Town Fox, Country Fox, Brian Vezey-Fitzgerald wrote:

Shropshire foxes are said to be particularly prone to lying-up in trees – on one occasion three were dislodged from the same tree…”

Foxes will also climb on to building roofs both to rest and search for prey. In a 2004 paper to Western North American Naturalist, James Sedgwick and John Bartholomew documented just such behaviour; they observed two young foxes 9.5m (31 ft) above ground on the roof of a domestic animal building in Fort Collins, Colorado. Outside of the city, foxes will often take over the disused burrows of other animals (especially rabbit burrows, which they extend to suit their size) or use existing structures such as rock caves, scree piles, wood piles, etc. In a survey of fox earths in various habitats around Saarbrücken in western Germany, Darius Weber found that foxes dug 44% of the earths themselves, with the rest either being the work of other animals, or situated in bunkers, caves or craters. In this study, the foxes frequently used rabbit burrows or badger setts; the use of the latter by foxes has been well documented in Britain and Europe.

Brian Vezey-Fitzgerald, in his 1968 Town Fox, Country Fox, points out it is widely reputed that badgers will vacate setts if a fox moves in, because they cannot put up with the smell or mess that the latter make; this may be true in some cases, but there are a considerable number of examples where the two species have shared (albeit different parts of) the same sett over successive generations. In their 1996 book, Badgers, Ernest Neal and Chris Cheeseman note that, although foxes occasionally dig their own dens they are typically "lazy diggers and much prefer to use badger setts if available". Moreover, Neal and Cheeseman point out that, in the Netherlands, Switzerland Denmark and Germany, "it is the rule for foxes and badgers to live in the same sett" – it has been postulated that this reflects a lack of suitable habitat in these countries. Similarly, in his 2010 book Badgers, Timothy Roper suggests that the increase in foxes observed during a badger culling trial may have been a response to an increase in the number of suitable vacant setts in which the foxes could raise their cubs. That said, Roper does note that:

Badgers and foxes are more tolerant of one another than is sometimes assumed, and it is not unusual for a large main sett to contain breeding females of both species.”

This relationship seems to work well and the badgers -- despite apparently being the dominant residents (they can apparently evict foxes at will) -- tolerate foxes for most of the year. The situation can, however, change when cubs are present. Intriguingly, whoever has cubs seems to get movement rights. One example of this comes from a wildlife park in Avon, where expansion of an earth by foxes had caused the amalgamation of the foxes' earth and a nearby badger sett. In this case, foxes were only dominant when they had cubs. When badgers have cubs underground, any encroachment by a fox typically meets with strong aggression on the part of the sow.

The construction of earths by foxes can affect other species in the vicinity and Polish botanist Artur Obidzinski has spent much of his time looking at how fox earths change the local ground flora. In a 2006 paper to Polish Botanical Studies, Obidzinski and colleague Piotr Kieltyk reported that the presence of fox earths caused local changes in the composition of the herb layer, limiting the development of plants by burying their above-ground parts, damaging root systems and trampling leaves. Uneaten food left lying around by the earth’s inhabitants was found to increase soil fertility and pH (i.e. make it less acidic) and foxes moved in seeds on their fur and in their scat; they also activated dormant seeds while digging.  Overall, Obidzinski and Kieltyk found more plant species in the vicinity of the earths than the surrounding, undisturbed, area.

How intensively an earth is used will depend on the season, habitat and the individual fox. In most cases, foxes tend to use earths only while rearing cubs or during particularly bad weather (i.e. heavy snowfall). In his chapter on the Red fox in the 1970 BBC book Private Lives: Studies of birds and other animals, Roger Burrows noted a difference in den use between the sexes, with vixens spending much of the winter in the ‘relative comfort’ of the earth, while dogs seldom, if ever, used earths, preferring instead to lie-up above ground. Studies on Bristol’s foxes have shown that males very rarely use an earth; normally it is only inhabited by the vixen and cubs, such that the dog’s first contact with his offspring is when they emerge from the den at around four weeks old. The vixen and cubs use the earth for around four months, after which the foxes tend to spend most of their time lying up in nearby vegetation during the day. Indeed, for most of the year, foxes seem to prefer to lie-up in vegetation, rather than using an earth and, in urban Melbourne, Marks and Bloomfield found that almost 80% of resting periods were spent sheltering in exotic weed infestations (blackberry, fennel, thistle, etc.). It seems that, along with harsh weather conditions, the amount of available cover also determines how likely a fox is to use an earth.

Between September 1989 and February 1992, Jean-Steve Meia and Jean-Marc Weber at the Université de Neuchâtel in Switzerland radio-tracked seven adult female foxes in the Swiss Jura Mountains. Their results, published in the journal Acta Theriologica during 1993, showed that the foxes seldom rested at a den site during the night (only 1% of observed resting periods were in dens), opting instead to lie-up in cover -- such that they were hidden -- close to where they had been active. During the day, however, three females frequently used dens, while the remaining four seldom used them. One vixen raised cubs during the study and was located in an earth during this time, but spent the majority of her time outside the cubbing season resting above ground. Interestingly, Meia and Weber found a positive correlation between the amount of open ground and the time spent resting in an earth, suggesting that foxes may use earths more often in habitats with little or no secure cover. The foxes also used only a few of the dens within their home range and there was no relationship between the number of earths in the territory and the number used by the territory holder.

Interestingly, Meia and Weber also found that weather (with the exception of extreme weather, notably snow) didn’t influence whether the foxes used an earth. In 1989, French biologist Marc Artois suggested that foxes avoided rain because it upsets their insulation (wet fur sticks together and is a very poor insulator) and both Stephen Harris and Huw Lloyd have noted that foxes prefer to lie in earths during bad weather. Meia and Weber, however, often observed foxes resting in totally open areas in heavy rain during the night. I too have seen a fox resting by a hedge, seemingly unconcerned by the rain and have watched foxes hunt during heavy rain and falling snow. Finally, this Swiss study noted that foxes often moved from one surface resting site to another for no apparent reason (i.e. weren’t disturbed) – given that resting and den sites were often situated at the periphery of the home range, the authors suggest that this may be the foxes resting as they patrolled their territory.

Fox rest in compost heapOrdinarily, foxes will seek out favoured sites within their territory that provide secure cover (high cereal crops or grass, reedbeds, bramble, bracken, etc.) in which to rest, but they will also hollow out temporary resting sites in some unexpected places. I have seen photos of a fox ‘rest’ dug into a compost heap (I presume the decomposing vegetation provided a valuable source of warmth and insect prey - image, right), another in a large haystack and also a pair of foxes lying among the ashes of a bonfire during very cold weather. In areas of high disturbance or where foxes are heavily persecuted they will often opt for resting sites that provide a good view of approaching danger and, in urban areas, such places tend to be shed roofs, but boulder scree is popular among hill foxes. Between January and May 1990, Ray Hewson studied the use of earths by two young vixens living in the hills of north-west Scotland. He found that they showed a preference for resting sites at a high vantage point with a good view of the surrounding area and where the foxes could move in and out of the earth under the cover of boulders. Similarly, in Cumbria, David Macdonald found that most daytime resting sites of foxes were in boulder scree, from where they had a good view of their surroundings; a minority were in peat holes, in which it was difficult for them to spot people sneaking up. In a recent study of space use by foxes in the southern German district of Starnberg, Christof Janko and colleagues at the Technische Universität München found that they used up to 10 resting sites situated throughout their home range; almost two-thirds (62%) were located in forests, while 21% were in reedbeds and 15% were in gardens. The researchers found no significant difference in the resting sites chosen by males and those chosen by females.

There is some suggestion that foxes show a preference for certain ‘directions of resting’, associated with how deeply they’re sleeping. In a curious paper to Behavioural Processes during 1979, Günter Tembrock described the choice of resting side in a group of 15 captive foxes, finding that:

“… the preferred direction of the resting position (curled up to the right or to the left) is not accidental. For all foxes considered, the preference for the left position is significant.

In fact, when the group was split up according to sex, it transpires that only the males showed a statistically significant preference for resting side. Moreover, dominant males were significantly more likely to lie on their left-hand side than subordinate animals and this preference seemed to develop at around seven months old. Tembrock suggested that foxes were more alert when lying on their left side of their body (i.e. they could react quicker to an approach) than when on their right side, although why that should be so is unclear. Whether resting on their right or left, there are several stories attesting to just how deeply foxes can sleep. During his studies in Bristol, Carl Soulsbury noticed that the signal from one fox hadn’t moved for eight hours and, the following day, he went to recover what he thought was the fox’s body, only to find a very much alive animal apparently aggrieved at being woken up! I know several photographers that have stumbled across a sleeping fox that hasn’t been woken by several minutes of photo-taking. While sleeping, it seems that foxes take comparatively few breaths and, in his book Wild Fox, Roger Burrows recounts how, on 29th February 1964 at 4pm, naturalist Trevor Walsh happened upon a fox curled up asleep on the Cotswolds, near Stroud. Mr Walsh watched the fox and counted 12 breaths in five minutes; this is an average of 2.4 breaths per minute or one breath every 25 seconds. According to Burrows, this compares to around 10 per minute for a sleeping human or domestic dog (one every 6 seconds), suggesting either that foxes have a more efficient oxygen extraction mechanism, or they can lower their metabolism further than either dogs or humans.

Although dog foxes rarely use earths, vixens may occasionally share them with other females, either simultaneously or asynchronously (i.e. use the same earth or rest site at different times). David Macdonald, in his 1987 Running with the Fox, described how a vixen regularly used the same earth throughout the winter, occasionally sharing it with one or two other vixens. Burrows considered that vixens lie up underground from November to March, possibly sharing an earth, while Meia and Weber observed that several individuals used the same resting sites, although they don’t say whether they did so at the same time. During his study of hill foxes, Hewson found that the two vixens had their own ‘exclusive’ resting sites as well as those that they shared with each other, although rarely on the same day. It has been suggested that much of the social interaction between members of a fox group occurs at resting sites, so it is presumed that any sharing of earths or rest sites is between family members.

Finally, it is worth making a brief mention of rest site fidelity – that is, how ‘faithful’ foxes are to a given spot. In a 2003 paper to Acta Theriologica, a team of biologists at Bristol University -- led by Tabetha Newman -- presented their analysis of resting site fidelity among foxes in the north-west of the city, before and after the outbreak of mange that decimated the fox population during the mid-1990s (i.e. comparing high and low population densities). The researchers looked at radio-tracking data and found two major shifts associated with the dramatic decline in fox numbers: they were less faithful to rest sites, and they chose different areas in which to rest. Before mange arrived a fox would spend 80% of its inactive time at a regular rest site, being found in a single ‘favourite’ site about half the time. Once the population had crashed, the researchers found them at regular rest sites only 15% of the time and, of this time, just under 20% of ‘fixes’ were at a single favoured site. In the pre-mange years, foxes spent most of their time resting in back gardens (particularly under sheds), with allotments, woodland and grassland coming in joint second. In the post-mange years, however, foxes seldom chose to rest in gardens (rarely being found near a shed), much preferring allotments or woodland – they opted to rest in badger setts or thick patches of bramble. The biologists suggest that when the fox population was high, foxes were forced to rest in the same site frequently and in locations that may not be their first choice because space was at a premium; when numbers dropped, foxes were free to rest where they wanted. Changing rest sites more frequently may also have helped the remaining foxes control parasites, such as the mange mite. (Back to Menu)

Red Fox (Vulpes vulpes)

Senses: Foxes are superb hunters with a finely-tuned battery of senses that allow them to interpret the world and respond accordingly to catch their prey. Curiously, despite having been farmed and studied for decades, there are surprisingly few empirical studies on fox sensory biology; much of the information we currently have is either based on behavioural observations or extrapolated from dogs.

Red fox eyeVision
Anyone who has watched a fox flee from a disturbance in the field will have noticed how they move quickly through scrub and woodland, squeezing under fences and gates, making jumps over ditches, running along walls and fences and navigating through bramble; all this conducted at some considerable speed. All the forgoing implies that foxes have good visual acuity at short-range. My own experience watching foxes suggests that, at longer distances, they are good at picking out certain shapes and contrasts (i.e. the human form on the horizon but not against a low contrasting background such as a tree or hedge) and, at any distance, they’re very sensitive to movement. Several authors have noted how a hunting fox will often walk straight past stationary beetles or crouching rabbits, suggesting that their vision (or certainly their hunting instinct) is based largely on movement. Indeed, foxes probably have a fairly low-resolution visual system that may make the hunting of small, stationary objects that cannot be isolated by either smell or sound, almost impossible. The reason for this, as we shall come to shortly, lies in the type of cells predominant on the retina. The subject of whether foxes see in colour is covered in a separate Q/A, but it is worth briefly looking at the more general aspects of their visual system.

Foxes are, in visual terms, arrhythmic (or 24-hour) mammals, meaning they can be active at any time, day or night (compare this to most squirrels, who are almost totally blind at night and can only be active during daylight). There are several adaptations that allow for this activity pattern; all help control the amount of light available to the animal. Foxes, unlike most canids, have vertically-slit pupils, which provide them with two significant advantages over hunters with round pupils. Primarily, vertically slit pupils can be closed more tightly than rounded ones and this, in conjunction with eyelids that close horizontally, allows their owner to more precisely regulate the amount of light entering the eye, helping them hunt across a wide variety of different light conditions. Additionally, vertically slit pupils may help the fox pinpoint horizontal movement. In a 1907 paper on ‘slit-form pupils’ Toronto University psychologist William Abbot suggested that a vertically-slit pupil may help a predator to focus sharply on small, ground-based prey as it moves laterally along the horizon. The iris of an adult fox is typically a stunning bright amber/yellow colour, owing largely to the pigment lipochrome (other factors such as the cellular structure, texture and pigment combinations control the precise colour and brightness); it is unknown what, if any, benefit foxes get from having an iris this colour, but it has been suggested that in some mammals (squirrels, for example) it may act in a similar manner to sunglasses, reducing glare in bright light. So, these features can help control the amount of light entering the eye during daylight, but foxes also have a neat anatomical feature that helps to boost the light available at night.

Foxes, like many animals, have a tapetum lucidium (from the Latin meaning ‘bright tapestry’), which is a collection of highly organized reflective cells (called leucophores) that form a layer behind the retina. There are several different types of tapetum, classified according to the structure and arrangement of the cells; the specifics don’t really matter to us, but foxes, like other carnivorans have a choroidal tapetum cellulosum. The cells of the tapetum are rectangular in shape and contain reflective material varying in size and shape; these cells are retroreflectors, which means they reflect light back along the same path it arrived on. Basically, this means that light passing through the retina (that in humans is lost) is reflected back into the eye, improving the night-vision of the fox. The fact that the light is reflected back along the exact same path it comes in on helps maintain the sharpness and contrast of the image on the retina (although there is probably still some blurring). The tapetum is also responsible for the eye-shine that is a familiar sight for anyone who’s ever shone a torch into a field at night or taken a flash photo of their pet. Humans lack a tapetum so in flash photos the light is reflected back by the blood in the retina (causing the red-eye that blights many party photos). In foxes (and most other mammals, for that matter), the tapetum bounces the light back into the eye and gives the impression that the eye is glowing – it isn’t glowing, merely reflecting light back at you. I am often asked what colour fox eye-shine is, but this is no fixed colour because this phenomenon is a form of iridescence – in other words, the colour of the reflected light can vary depending on the angle from which it is viewed. Nonetheless, in my experience and that of others, eye-shine tends to be blue or green, although yellow/orange or red is sometimes reported. Interestingly, I have heard it suggested that cubs or subadults have a different eye-shine colour to adults (green or dull yellow compared with bright yellow or red) and in my experiece, cubs often display a turquoise/blue eyeshine. Part of any difference between the cubs and adults may be a result of the cubs being lower to the ground than adults (affecting the angle of reflection), but it may also be related to the development of the tapetum. I know of no data for foxes, but in cats and dogs the tapetum isn’t fully developed until the animal is about four months old.

There are two main types of light detecting cells on the retina of the fox: rods and cones. The two cells differ in various ways; most notably in their sensitivity to light and how they’re wired into the brain. Rod cells contain a single pigment, called rhodopsin, which is sensitive to ‘blue/purple’ light (peak sensitivity at wavelength 496 nanometres); consequently, rods cannot discriminate between colours and are used only for determining brightness. (I should point out that light isn’t coloured, it’s all just photons. The reason it appears coloured is because different frequencies of photons stimulate different retinal cells and our brain interprets this electrical impulse as red, green, or blue.) Moreover, the rod cells themselves are very sensitive to light and several are attached to a single neuron. The result is that the cells can be stimulated by only a few photons (particles of light) and several rods can act together to stimulate a single neuron (sending an electrical signal to the brain, which is used to build an image). The brain cannot, however, tell which of the cells in the ‘rod bundle’ was stimulated, so it can’t interpret the exact size or shape of the object being looked at. In essence, the rod system is a high sensitivity but low acuity system – it’s superb for letting the animal pick out objects in low light (such as that around twilight and at night), but the picture the animal sees is colour-less and lacks detail. Cones, by contrast, are almost the exact opposite: they work in bright light, there are fewer per neurone (one per neurone in some parts of the retina) and they contain different pigments that allow the perception of colour. Among mammals there are three ‘types’ of cone cell (they look the same, but contain different light-sensing chemicals, called photopsins or photopigments): those that detect long-wave (red) light (L cones); those that detect medium-wave (green) light (M cones); and those that detect short-wave (blue) light (S cones). Cone cells are less sensitive to light than rods, so more photons must strike them before they are stimulated to send a message to the brain – the result is that they need relatively bright light to function (making them useless at twilight or at night), but in return they can detect more detail and register rapid or subtle changes in an image that rods would miss.

Ultimately, if you had a retina composed entirely of cones you’d be great at spotting things and recognising objects during the day, but blind in dim light. Conversely, rod cells become saturated in light levels much beyond those produced by a 20-watt light bulb, making them useless during the daytime. Consequently, animals that are active during the day and night have a retina with both rod and cone cells; the systems swap over as light levels rise and fall. Sometimes this swap over is quick (i.e. when cones take over from rods as you move from a dark place to a bright one it takes only a few seconds to restore vision), while at other times it is much slower (i.e. when rods take over from cones as you turn off a light a night). Foxes have a retina dominated by rods, but with a few interspersed M and S cones (no L cones, so they are essentially red-green colour-blind) arranged in concentric rings, or zones, on the retina – this setup is referred to as a multifocal optic system and helps the fox maintain colour vision in very bright light. Different colours of light are focused on different zones of the retina (hence the multifocal name); the slit pupil allows all the various zones to be used, even with the pupil reduced in size (see diagram). So, having a multifocal optic system means that, even in very bright light when the pupil has been closed down, some colour perception is still possible and this colour information can be used to resolve details in the image.

Fox Eyes
The eyes of the Red fox exhibit a vertically-slit pupil (left), allowing precise regulation of light entering the eye, and a layer of reflective cells at the back of the retina that reflect light back into the eye and improve vision in low light conditions; this also produces the eyeshine. Above, shows the golden eyeshine of an adult vixen (middle) caused by a direct flash and the turquoise/blue eyeshine of a cub (right). Photo credits, left to right: David Pressland; Paul Cecil; Paul Cecil.

Essentially, a fox’s vision is adapted for twilight (crepuscular) and nocturnal activity. I’m not aware of any equivalent data on foxes, but it has been estimated that cats (which possess a similar eye structure, pupil and tapetum to foxes) can see in low light five-or-six times better than humans. (It should be mentioned that light is an essential component of the visual process, and no mammals can see in total darkness.) So, the large number of rods along with the tapetum give foxes much better night vision than we have, but they also have sufficient cone cells and a strictly controlled pupil that allow hunting during the daytime too, even if the picture they see is less detailed or colourful than the one we see.

I have mentioned that field observations suggest foxes are myopic (short-sighted); it can run through vegetation without incident, but will approach stationary objects to within a few metres unless another sense alerts it to danger or the object moves. Our understanding of the anatomy of the visual system seems to support such observations. Focal length is a mathematical function of wavelength; don’t worry about the specifics, all that matters is that depth of field (i.e. the size of the area of an image that’s in focus) is smallest for short (blue) wavelengths and largest for long (red) wavelengths. Having a retina dominated by rods (which are sensitive to short wave light) and lacking L cones altogether would certainly suggest that foxes are short-sighted. Moreover, in Town Fox, Country Fox, Brian Vesey-Fitzgerald notes that fox eyes lack a macula lutea -- the highly sensitive central part of the retina, containing the fovea, responsible for our perception of detail (without it, reading this website would be impossible) -- which means that foxes are unable to focus on stationary objects for more than a few seconds, again rendering them myopic. Finally, despite being short-sighted, foxes apparently have generally lower focusing power than we do.

In his The Red Fox, Huw Lloyd presented diagrams of the fox’s visual field and, based on these drawings, they have a field of view spanning roughly 260-degrees, with a blind-spot covering about 100-degrees directly behind their head and an overlap of fields of the right and left eyes of about 40-degrees (the degree of overlap is referred to as binocular vision and allows animals to judge distances). To put this in context rabbits have a visual field of about 360-degrees (they’re only blind to a 10-degree area directly in front of their nose), but have a binocular overlap of only about 20-degrees; this makes them good at spotting foxes and photographers sneaking up on them, but poor at telling how far away the danger is. You, by contrast, can see objects within a horizontal arc of about 180-degrees directly in front of you (without moving your eyes or head), but about 140-degrees of this field is binocular overlap, making you very good at judging distance. So foxes have some binocular vision (more than rabbits, but substantially less than us), which is useful for scaling fences and chasing down prey. Lloyd also calculated the optic axis of the fox (this is the angle that the eyes look out relative to an imaginary line drawn down the middle of the body – see diagram) to be about 15-degrees, which means that their eyes cannot converge on a near object as well as ours can (humans have an optic axis of about 5-degrees). Overall, Vezey-Fitzgerald probably wasn’t too far off the mark when he suggested that foxes use their eyes to avoid objects, not recognise them!

Red Fox Eyeshine Colours
Red fox feeding on bread in a garden. Notice that the right eyeshine is green, while the left eyeshine is red - this illustrates how the angle of the reflected light affects the colour of the eyeshine you see.

So, with this in mind, is vision an important sense for the fox?  After all, it is not uncommon for old foxes to develop cataracts and at least one, other-wise healthy, blind fox was radio-tracked by the biologists in Oxford. In 1964, Finnish biologist Henrik Österholm published a paper in Acta Zoologica Fennica in which he assessed the role played by the fox’s various senses during hunting. Österholm concluded that vision is a key factor in finding food during daylight but it became less important at dusk and in the dark, when the fox relied more on hearing. Overall, it seems that hearing was the most important sense, followed by vision and then smell – even at twilight, vision appeared more important than smell to the hunting fox. Österholm also briefly tested for colour discrimination, using both squares of coloured (blue and green) card and different coloured porcelain eggs. He found that colour had no significant impact on the test foxes, while they all responded to the brightness of the eggs used (which is expected, given the domination of the rod cells in the retina); light eggs (e.g. white) were always preferred over dark (blue and red) ones, presumably because these were closer to the hue of a natural egg. Interestingly, Österholm found that although brightness was an important consideration, it was apparently subordinate to size and shape, concluding:

If an object has the right quantities of size and shape it will be taken independent of the colour.

Finally, on the subject of the importance of vision to hunting foxes, it has recently been suggested that foxes may be able to see the earth’s geomagnetic field (GMF) and use it to zero in on their prey thereby improving their hunting success. In a fascinating paper to the journal Biology Letters during 2011, a team of biologists at the Czech University of Life Sciences and the University of Duisburg-Essen in Germany reported their observations of 84 mousing bouts (where foxes jump high in the air and land on their prey, usually small rodents) in 65 locations across the Czech Republic between April 2008 and September 2010. The biologists found that there was no significant difference between the direction in which the fox was facing when it pounced (the directional heading) and prey capture success when the fox could see its quarry. When the fox was hunting in long grass or snow, however, and couldn’t see its target, the researchers observed that three-quarters of successful pounces occurred when the foxes were facing north-east -- this was regardless of the time of day, wind direction or cloud cover -- with less than one-fifth of pounces facing any other magnetic alignment being successful. The biologists suggest that:


It is suggested that foxes, like many other animals, may see magnetic north as a shadowy ring; the fox could then line this ring up with (i.e. superimpose it over) the direction from which it hears its prey rustling. It may help to visualise this. Imagine wearing a miner’s helmet (a hard hat with a torch attached to the front); the torch points at an angle, illuminating a spot on the ground two metres (6ft) in front of you. Wherever you walk, that spot of light is always two metres ahead of you. Now, imagine that you hear something moving in the darkness and walk towards it until it’s in the beam of your torch – you now know that the object is two metres from you and, if you’re a fox and that object is a mouse, how far you have to jump to catch it. The authors suggest that foxes do the same thing; they align this ring up with where they hear the rustling coming from (like a target bulls-eye) and then they know how far away dinner is.

Slit Pupils
The functional significance of a slit pupil over a circular one. The coloured rings show areas on the retina where different colours of light are focussed and we can see how as the circular pupil contracts (i.e. from A to B) we lose one colour from the image. When a vertically (or horizontally) slit pupil contracts (i.e. C) the light entering the eye is reduced, but all colours remain. Diagram originally published as part of a 2006 paper to the Journal of Experimental Biology by Tim Malmström and Ronald Kröger and is reproduced here with Dr Kröger's permission.

In summary we can say that the fox has some capacity for colour vision along with various adaptations that allow them to hunt in almost any light conditions. They have a relatively wide field of view, but limited binocular vision and focussing power. Their vision is heavily based on movement and this is more so during the day than at night. More rods are plugged into a single nerve than cones, so it takes a larger movement to register a change in the picture when the animal is using only their rods (at night) than when they’re using their cones (during the day). The need for a big change/movement and the limited focal power of the eye makes hunting small, stationary objects by sight alone very difficult, if not impossible, for the fox. (Back to Menu)

Alert Red foxFoxes have two highly mobile ears, the rigid ‘flaps’ (technically called the auricle or pinna, but sometimes referred to as ‘trumpets’) of which serve to catch and funnel sound down into the ear canal. The ears can be moved independently, allowing them to pinpoint the source of a sound. My observations suggest that Red foxes can rotate each ear by about 150-degrees in a single direction -- the right ear rotates clockwise and the left ear anticlockwise -- in order to pick-up sounds to the side and behind them. The ears are furred both on the back (with short hairs) and internally, with relatively longer hair – the function of this inner ear fur is presumably to help trap particles of dirt, preventing them from entering the ear canal. The ears are spaced apart, with the gap between them (the interaural or tympanic distance) varying according to sex, and from individual to individual; this separation means that sound coming in from either side will register in one ear fractionally sooner than the other, and the fox soon learns how to use this delay to pinpoint the source of a sound. The interaural distance in adult Red foxes is about three centimetres (just over an inch), which means that -- given various waveform properties that I don’t plan to elaborate on -- sounds between 5.5 and 11 kHz (see below) should be most difficult for them to locate.

Fox hearing is very sensitive to low frequency sounds; the rustling noises made by prey. When we talk about how well an animal can hear, there are two results that tend to be presented: the audible frequencies and the minimum audible angle (MAA). Audible frequencies are the sounds that an animal can hear. Sound travels through the air in waves that peak and trough in a similar manner to waves on water, with one peak and trough considered a ‘cycle’; thus, a sound is described based on the number of cycles per second. Units for sound measured in this way are called hertz (abbreviated to Hz) and values are sometimes reported as kilohertz (kHz), meaning thousands of cycles per second; so 14,000Hz is the same as 14kHz. High-pitched sounds (such as the ‘treble’ on your stereo) have more cycles per second than low-pitched sounds (such as ‘bass’). In addition, scientists studying hearing often try to measure how good their subject is at telling a sound has moved from directly in front of them (a zero-degree angle): this is the MAA. Under ideal conditions, humans tend to be able to distinguish sounds moving by a single degree either side of them, while Fox squirrels, for example, have been shown to have MAAs of about 14-degrees. In other words, humans can tell a sound is no longer ‘dead ahead’ when it moves to either side by only one degree, while the sound must move 14-degrees to either side before a Fox squirrel would know it was no longer straight in front of them. So, in essence, the smaller the MAA, the more sensitive the animal is to the movement of a sound source (be it a speaker or a rustling vole). One final point to note is that high frequency sounds are more readily ‘dampened’ by the air and interfered with by objects in their path (a process known as attenuation), making them more difficult to pinpoint than low frequency ones.

Henrik Österholm was one of the first biologists to systematically study the hearing capabilities of Red foxes, by using sound to guide his captive animals to a food reward. Österholm found that foxes could locate the food at all frequencies used (from 300 Hz to 15 kHz), but at higher frequencies an MAA of 10-degrees or greater was required. Between 300 and 700 Hz the foxes were almost spot on target (in at least 90% of cases they pinpointed the object), while they could locate the sound source to within 1-degree at frequencies between 700 Hz and 3 kHz. Foxes located the sound to within 2.5-degrees up to 15 kHz, after which they were less accurate. The striking trend in Österholm’s data is that the foxes were less accurate at locating the sound source as the frequencies increased and, overall, they were most sensitive to sounds of about 700 Hz. Eleven years after Österholm’s work, Michigan State University ecologists Thomas Isley and Leslie Gysel published a paper in the Journal of Mammalogy in which they presented data on how well nine captive foxes located sounds of between 300 Hz and 34 kHz. The researchers found that the accuracy with which foxes located the sound increased gradually to 3.5 kHz, at which they were most sensitive; this is the frequency of sound produced by gnawing and rustling rodents and the calls of some gamebird chicks. Beyond 3.5 kHz the foxes were less accurate at finding the sound although, overall, they located sounds between 900 Hz and 14 kHz with at least 90% accuracy. Isley and Gysel noted that their animals had most trouble locating sounds at 300 Hz, 600 Hz, 18 kHz and 34 kHz, although even at 31 kHz the foxes found the target 71% of the time; they also noted dips in sensitivity at 8.5 and 11 kHz. To give these results some context, humans (depending on age) generally hear in the region from 15 Hz to 20 kHz, with peak sensitivity between 2 kHz and 4 kHz, the frequency of human conversation.

The different peak frequencies found by the different studies is interesting and may reflect that the Michigan biologists were using pure-tones, while Österholm’s sounds were impure (i.e. had a mixture of tones). This highlights that we must be careful when applying laboratory studies to the fox in the field.

For foxes, sound is important for various aspects of their daily lives. It is crucial for hunting and, Österholm considered that:

“… hearing has distinctly the greatest significance for locating the prey.

Indeed, anyone who has watched a fox hunting in long grass will probably have noticed that the animal appears attracted by rustling among the vegetation, which it then seems to track by twitching and rotating its ears before pouncing. David Macdonald, in his experiments with a hand-reared vixen, found that she often caught undesirable small mammals (shrews, for example) because she didn’t know what she’d found until after pouncing and killing the prey – in other words, the fox was hunting largely by sound. Macdonald notes that beetles are caught in much the same manner, with one unfortunate insect being tracked down from 10 metres (30ft) away. Most hunters will attest to how foxes can be ‘called’ in from considerable distance using lures (whistles or squeakers that mimic the call of a favoured prey). All this points to the importance of sound to the hunting fox. Still, sound is important for other aspects of fox life too. Foxes communicate, over both long and short distances, with sound and also use it to recognise possible danger. In his Town Fox, Country Fox Brian Vesey-Fitzgerald, who considered foxes to have better hearing than domestic dogs, told how a vixen he was watching apparently heard a man approach on soft earth some 30 seconds before he came around the blind bend 83m (272 ft) from the den. (Back to Menu)

Red fox noseSmell
There are very few studies presenting empirical data on the fox's olfactory capabilities, and I’m not aware of any statistics on the number of receptive cells in the nasal epithelium or estimations of how many times better a fox’s sense of smell is over our own. Nonetheless, behavioural experiments and field observations suggest that foxes have a very keen sense of smell. We know that scent plays a very important social function (see Q/A), being used both to identify individual foxes and mark out territory boundaries. Additionally, many authors have written about how foxes have dug up the carcasses of livestock buried several inches below the surface or covered by deep snow. Some naturalists have written of the fox’s ability to seemingly tell strangers from regular fox-watchers on the basis of scent alone. Vezey-Fitzgerald, for example, described how a vixen living in an earth opposite his house was used to the comings-and-goings of the local people but would suddenly freeze and ‘clap down’ when she caught the scent of a newcomer to the neighbourhood. My experience suggests that foxes spend a good deal of their time following their nose, which is constantly kept moist, thereby aiding not only the detection of scent trails (it has been suggested that wet noses help improve scent detection by dissolving the chemicals in the odour trail), but also helping the animal tell the wind direction.

Foxes, like most mammals, possess turbinates -- convoluted bony structures in the nose that, as well as regulating the airflow within the nasal cavity, serve to increase the surface area of the olfactory epithelium -- and, as a consequence, the small snout can contain a considerable mucosal area. In essence, the larger the mucosal area, the greater the surface available for scent molecules to land on and the better the sense of smell. I'm not aware of any morphological studies documenting the nasal epithelial area in foxes, but domestic cats have about 21 sq-cm (3 sq-in), while a small dog -- a Cocker spaniel, for example -- has close to 70 sq-cm (11 sq-in). A fox probably lies somewhere in between; either way, this can be compared to humans that have, on average, 5 sq-cm (three-quarters sq-in).

During his studies on captive foxes, Österholm found that his subjects couldn't find the pieces of meat he'd buried in a 10cm (4 in.) deep hole until they were within half a metre (2ft) of it, while pieces of meat sitting on the ground were only found when the fox was within two metres (7ft) of them. These results suggest that a fox's sense of smell is rather limited. In his 1980 book Red Fox, however, H. G. Lloyd argued that Österholm’s studies, which used fresh meat, might yield different results if they were conducted with decaying flesh (given that foxes are well known to scavenge and fresh meat has comparatively little smell). Foxes also possess a Vomeronasal Organ (sometimes referred to as Jacobson's Organ after the German anatomist who is often, erroneously, credited with its discovery), which opens into the roof of the mouth and is composed of tissue very similar to that found in the nasal lining; most mammals possess this organ and it appears to play a role in scent (especially pheromone) detection. Some work has been done on the gustatory (taste) sense -- which is an extension of the olfactory sense -- of foxes and, in 1886 American doctor Fred Tuckerman described the tongue of the Red fox. Tuckerman’s data showed a tongue about 12cm (almost 5 in.) long and two centimetres (just under an inch) wide, with the texture of fine sandpaper, and suggested that foxes may have a less well developed sense of taste than we have, with fewer sour-sensing taste buds (vallate and foliate papillae). (Back to Menu)

Red Fox VibrissaeA characteristic of mammals is the presence of fur/hair, one function of which is to help maintain body temperature. Some types of hair, however, can also have a tactile (touch) function, allowing their owner to feel their way around. Foxes have long (up to about 11cm / 4.5 in.), stiff specialized hairs known as vibrissae, or "whiskers", on their muzzles and forelegs (around the carpal or 'wrist' joint), which are associated with special nerve cells that are extremely sensitive to any contact – if you brush against a pet dog or cat's whiskers, you'll notice them sharply turn their face away. The carpal vibrissae are thought to provide the animal with information on its body position while hunting. Studies of cat whiskers have found that the part of the brain that receives information from the vibrissae has a very similar structure to the visual cortex -- some authors have suggested that the same is true of foxes -- implying that it may help the animal build up a visual image of its surroundings, although they don't 'see' with their whiskers per se. Whiskers are embedded three-times deeper into the skin than other hairs and it has been demonstrated that, again in cats, when a prey item is too close for the animal to focus on it, the vibrissae are manoeuvred around the object so the cat knows where to bite. The whiskers also grow out to roughly the width of the body, so their owner is better able to judge whether they will fit through a given gap. As with cats and dogs, the fur between the pads of foxes is very sensitive to touch (and fox pads are themselves furred, unlike domestic cats and dogs) and probably plays a role in allowing foxes to navigate their way along thin fences, across boulder scree and through the branches of trees with apparent ease. Overall, the vibrissae and inter-pad hairs provide very detailed information on the objects that they touch, as well as detecting air movements that may help reveal the source of potential prey. (Back to Menu)

Territoriality and Home Range: For any animal trying to eke out a living in the wild there are certain resources that are essential; food, water, and shelter being the main ones. Now, it is highly unlikely that everything that you need will be clumped together just waiting for you to happen across it – rather, it’s almost invariably dispersed across a wide area and may be spread out between several different habitats (forests, farmland, villages, etc.). The area (often, although not always, around a suitable den/nest/shelter site) over which you spend your time wandering, looking for food and water, is loosely termed your home range. In some cases, you might want to secure the resources in this area for yourself (and possibly your family) and this would involve kicking intruders out of all or part(s) of your home range – these areas are what ecologists call territories. Thus, despite often being used interchangeably, a territory and a home range are not necessarily the same thing: a home range may overlap with other members of the same species, while a territory generally will not (note that intruders of the opposite sex tend to be tolerated more than same-sex interlopers). In some cases, perhaps in certain seasons, you may choose to defend the whole area against intruders and therefore it and your territory are the same, while at other times (such as when food is abundant) you may allow intruders in some or all areas. In essence, though, the home range is the area transversed by an animal during its normal activity (i.e. finding food, mating and caring for young) and a species is considered territorial if each individual (or group) constructs and defends an area from intrusion by other members of the same species.

While the size of an animal's territory is largely determined by the distribution of resources across the area, group size is determined by the average abundance of those resources (i.e. how many animals the resources in the territory can support). Consequently, territory size and group size may vary independently and there is no significant relationship between the size of a territory and the number of animals living in it. This is because a small, but rich, territory can support more animals than a larger, but poorer, one. During some seasons or years there may be more resources in the territory than the residents require and this means that other individuals (usually offspring) may be permitted to hang around. We will come back to this concept in the Behaviour and Sociality section when we look at how group living may have arisen in foxes, but in the meantime I mention it just as a sideline when discussing the flexibility that we see in the territorial system of the Red fox. Indeed, there is tremendous variation in both the territorial behaviour and territory size of foxes; from a complete absence of territoriality in some populations, to complete home range defence in others. Ergo, it is very difficult to come up with the size of an ‘average’ fox territory; if such a concept even exists. That which follows is an overview of territory sizes and ‘normal’ home range movements of foxes – the subject of how far foxes move when dispersing is covered in the associated Q/A. [Click here for a note on the use of areas]

It is now widely accepted that three main factors act in concert to determine the size and shape of the home range of a fox: food abundance; food dispersion; and location of shelters in relation to the main food patches. As a consequence, home range size varies widely: from about four hectares (ha) -- almost 10 acres -- in some urban areas, to 5,000 ha (50 sq-km or about 19 sq-mi) in desert regions, where resources are sparsely distributed. The largest territory of a UK fox that I have found so far is a dog fox in the Eriboll area of northern Scotland who ranged over 4,500 ha (45 sq-km or about 17 sq-mi). In his 1987 book, Running with the Fox, David Macdonald provides some examples of the huge variation in territory sizes:

Boar Hill (gardens and farmland) = 10-70 ha (averaging 40 ha)
Oxford’s mixed farmland = 100-250 ha
Wytham Woods (private Deciduous woodland) = 20-100 ha (ave. 60 ha)
Oxford city = averaged 90 ha
Suburban Bristol = 25-40 ha (increasing to 90 ha on council estates)
Dutch heathland = averaged 880 ha
Cumbria Fells = averaged more than 1,000 ha
Oman desert = stable range of 5,000 ha
Italian mountain meadows = 400-1,300 ha
North America = typically 600-900 ha
Barren cereal plains of North Dakota = up to 2,000 ha
Arctic = 3,400 ha

So, were we to generalise, we can see that home ranges in Europe typically cover between about 40 ha and 1,300 ha (up to 13 sq-km or 5 sq-mi). This area may contain a single fox, a pair of foxes or, commonly in Europe, small family groups consisting of three to six animals. Territories tend to be stable during the spring and summer, coming under increasing pressure during the autumn and winter as dispersal of cubs and long-range movements (in search of mates) increase; a difference less apparent among group-living foxes. Where foxes live singly, males seem to range over larger areas than females. In Edinburgh during the early 1980s, for example, Hugh Kolb found that average dog fox territories were 460 ha (just over 4.5 sq-km or almost 2 sq-mi), while vixens ranged over only about 150 ha (1.5 sq-km or just over half sq-mi). Similarly, in 1970, Roger Burrows suggested that vixens hold small territories with loose society (several females using the same areas, at different times to avoid conflict), while dogs actively defend a larger area that may engulf the ranges of several females. A study tracking foxes in the Netherlands found that males were significantly more territorially active than females. In contrast, however, a tracking study of foxes between May and September 1989 in central Kyushu in southern Japan found no significant differences between the territories of dogs and vixens.

English Farmland
Mixed (arable and livestock) farmland, with plenty of hedges and copses provides ideal habitat for the Red fox.

The question of how exclusive territories are (i.e. whether all, part or none of them are actively defended) is deceptively complex and the tremendous flexibility in fox society means there is no ‘one size fits all’ answer. In some cases, such as those encountered by David Macdonald while tracking foxes in urban Oxford, they never seem to trespass – in his Running with the Fox, Macdonald noted that neighbouring groups didn’t trespass, even where some groups had food put out in feeding stations that the others must have been able to smell. Thus, it would seem that, if you have several foxes visiting your garden at once, they’re likely to be members of the same social group. Macdonald considered that habitat type was an important factor in determining territory exclusivity and, in his book, he described how territory boundaries may be ‘hazy’ in rural (especially woodland) habitats, with neighbouring groups using the same clumps of trees and having paths that criss-cross. In urban areas, by contrast, streets provide clear demarcations of territories. He concluded that there was no trespassing in urban areas (where high-quality feeding sites were at stake, territory boundaries were sharply defined and meticulously observed), while deep in the woods (used mainly for sleeping by day) there was “more latitude for neighbourly tolerance”. This would certainly explain why, while tracking vixens in the Welsh mountains, Macdonald found that two neighbours occasionally used the same resting sites, although not at the same time. Studies on urban foxes elsewhere, however, paint a different picture. During 1978-79, for example, Stephen Harris tracked seven breeding vixens in Bristol, finding that they moved, on occasion, just over 300 metres (990 ft) outside their normal ranges and shared feeding sites with animals from adjacent groups. Harris concluded that, probably because the diverse pattern of food availability in urban areas is difficult to defend, the breeding vixens exhibited little, if any, territorial behaviour. Overall, the broad picture seems to be that foxes living in small ranges (at high densities) are more likely to maintain rigid territory boundaries than those living in larger ranges (at lower densities), although there is considerable variation between populations. Off-hand, it would seem logical that smaller areas are easier to defend than larger ones and this may be part of the explanation.

So, a territory can be large or small and may or may not be rigorously defended, but what determines its size and shape?  We have seen that habitat plays a crucial role in terms of both landmarks to use as borders and the availability of food, but there is another important factor only recently alluded to: the size of the animal. In a 2008 paper to the Journal of Mammalogy, a team of Bristol University biologists led by Graziella Iossa described how: “Increased body size in males appeared to confer an advantage in territory acquisition and defense…”. In essence, the biologists found that smaller males suffered more aggressive challenges for space (what the authors termed “boundary pressure”) than larger males and, as a consequence, tended to hold smaller territories. So, larger males held larger territories and made it more difficult for smaller males to secure space. Earlier work on the take-over of fox territories conducted by Eric Preston in a large fenced enclosure in North Dakota during the summer of 1972, found that it was almost invariably the resident males that tackled intruders and, rather than expulsion being rapid and violent, it was: “…a rather gradual exclusion resulting from continual harassment by the resident male”.  Preston’s findings are at odds with many of the observations that David Macdonald and Stephen Harris have made (both documenting rapid, violent expulsion of intruders – see Behaviour), but it does give an indication of how the boundary pressure from larger males described by Iossa and her team might operate.

Red fox on patrollGiven that territory size, shape and level of defence are dependent upon the availability and distribution of resources, it is not unexpected to find that foxes living in the food-rich habitat of the city tend to forage over smaller areas -- about 50 ha (half a sq-km or one-quarter of a square-mile) -- than their rural counterparts. There is, however, considerable variation in urban territory size and, in their 2010 overview of fox biology in Urban Carnivores, the Bristol University biologists give the following as territory sizes for urban foxes: 18-169 ha (Bristol); 54-93 ha (Oxford); 259 ha (Virginia, USA); 379-547 ha (Illinois, USA); and 420 ha (California, USA). Urban territories are generally small with little or no overlap but, as Harris has alluded to above, there are areas (those with abundant food) where animals from neighbouring groups may come to feed without any apparent hostility. In some cases, where food is particularly abundant, so many foxes may be drawn in that it becomes impractical to defend the area and the only option is either to leave or tolerate the intruders. Another result of high food availability and small territories in urban areas is that fox densities tend to be higher; more foxes mean more competition for space and, in a highly tumultuous environment such as the city, where lots of vehicle activity means foxes generally live for less than two years, we sometimes see an interesting feature known as territorial drifting.

Radio-tracking studies of foxes in Oxford city by David Macdonald and Patrick Doncaster during the late 1980s and early 1990s demonstrated that territories were arranged in a ‘honeycomb’ pattern and, although territories in the suburbs appeared spatially stable, the location of those in the city centre continually drifted. Moreover, the biologists discovered that the territories drifted in synchrony with each other (at a rate of about one territory per year) and, although the territories were reasonably small (averaging only 39 hectares – just under half sq-km or one-fifth sq-mi) they were constant in size. Thus, in Oxford city at least, it seems that as one part of the territory is yielded by fox "A", this area is taken over by one of its neighbours (fox "B"); but fox B doesn't range over a larger area, rather it relinquishes a similar sized area of its own territory. Doncaster and Macdonald suggest that: "the ultimate explanation for drifting is that the city environment is inherently disturbed, by pedestrian and road traffic, habitat management and construction and demolition work." It is an interesting thought that such drifting may not be solely the result of foxes dying, but may also be affected by their changing landscape. Indeed, given that conspicuous linear features (e.g. roads, hedges, walls, etc.) are often used as territory boundaries, it is easy to see how the continual state of development in our major cities could lead to the continual fluctuation of fox territories. It seems that there may also be some seasonality to this drifting and, in his 1996 review of the Red fox social system, Paolo Cavallini noted that sudden home range shifts were more common during June to December, while drifting was faster in winter. The picture in Oxford, however, doesn’t appear to be universal and, in the West Midlands, the exact opposite has been documented; with territories remaining stable for many years.

In Bristol, the arrival of sarcoptic mange offered an opportunity to see how the fox population responded to a drastic decline in numbers. Prior to the appearance of mange, territories of Bristol’s urban foxes were found to be stable across years, with little overlap. In early 1994, a young male infected with mange arrived in Bristol, having spent the winter outside of the city; the disease spread rapidly through the population, causing the death of some 95% of the resident foxes. Unlike the foxes Macdonald and Doncaster tracked in Oxford, however, Bristol’s foxes responded to the death of a neighbour by expanding their territory; essentially taking up the slack. The biologists at Bristol University’s Mammal Research Unit observed that, despite the increased level of food availability, foxes continued to expand their territories as neighbouring groups died; survivors took over this free space within a matter of days, enlarging their own territories until they came across an occupied territory. So, why would the foxes do this? They didn’t need the extra food (after all, their own territories before the die-off supplied them with more than enough) and a larger area is more difficult to defend, requiring more energy to patrol. The Bristol biologists suggest that the foxes may have been attempting to prevent new animals from settling in the area by monopolizing space. In addition, in the pre-mange period, some foxes were observed splitting their territories -- half being ‘given’ to the resident’s offspring -- and if you hold a larger area, any future splitting is simpler and less costly in terms of resource loss.

Red fox following hedge
Hedges are often used to delimit territory boundaries and foxes can often be seen travelling along them when patrolling and hunting.

So, fox territories may be very stable from year-to-year, they may drift as the habitat changes or they may expand as neighbours die. Additionally, some studies suggest that if a territory becomes vacant, and isn’t amalgamated into a neighbour’s range, the space is quickly filled by a new individual – studies by Andrew Wilson suggest that this happens within about a fortnight. How, then, do foxes stake out their territory? How does one territory holder know where their turf stops and their neighbour’s starts? How do residents let passersby know this spot is occupied?

We have already seen that foxes often use linear landscape features such as hedges, tree-lines, roads and so forth as territory boundaries, but the territory owner still needs to let others know this is their hedge and what happens when there’s no convenient feature? Given that permanent monitoring of territory borders isn't an option (foxes have much more pressing demands on their time), a conveinient signpost is required in the owner's absence; for this foxes use scent to signify occupancy, leaving scent marks in the form of urine and scat at strategic sites throughout their territory. I don’t plan to delve too deeply into this topic here (see Q/A), but essentially foxes leave scent marks on travel routes in proportion to how frequently they’re used and where in the social order the animal sits (dominant animals scent mark more than subordinates). Scats are most commonly used as territory markers, almost invariably -- about 80% of the time in some studies -- left on visually conspicuous objects (e.g. rocks, tufts of grass, garden gnomes, etc.); scats make more obvious and more robust signals than urine. Fox urine, scat and the secretions from the paired anal glands (which is deposited on scats that the fox wants to use as territorial markers) contain hundreds of chemical aromas that convey a wealth of information about the individual who left it, as well as how long ago it was made. We know, based on work by Janosch Arnold for his Ph.D at Bristol University, that fox scent marks contain information about the sex, season, relatedness, health and probably the social status of the animal who left it. It has also been suggested that resident foxes may recognise territory boundaries by the presence of ‘alien’ urine.

Red fox cocking legWorking with his captive vixen, David Macdonald found that the frequency of scent marking fell as you approached the border of her territory (where she would pause for a few seconds before spontaneously turning back). Macdonald described how the exact turning point could be changed by introducing a sample of alien fox urine near the border. If the alien urine was introduced just inside the boundary of her territory, she’d turn back when she smelled it (but would ignore her own transplanted urine), even if the area further on had previously been part of her territory. There was a limit, however, and if the alien sample was introduced elsewhere in her territory -- i.e. not near the border -- it was over-marked (urinated on top of) by the vixen. So, it seems that foxes scent mark most in the core of their territory -- where they’re most active -- and less frequently at the periphery, with foxes having a fairly good idea where their territory ends based on where they expect to encounter foreign urine. Scent isn't, of course, a permaneant feature in the environment and after a while it gets degraded by rain, wind, etc. (with some, such as scat, being more robust than others). Consequently, the owner of the territory must revisit territory boundaries frequently to reapply the scent - at the same time, failing to do so will result in a weaker scent and might suggest to an intruding animal that the owner is either no longer around, or rarely visits this particular part of their range. Indeed, Macdonald, in a 1980 paper to the Symposia of the Zoological Society of London, suggested that the strategic placement of these scent marks may allow an intruder to chart a “safe” route through a territory by ‘reading’ fresh urine marks; thus avoiding the resident. Generally speaking, neighbouring territory holders have little to gain from fighting with each other (each territory has sufficient resources to support the animal and the potential costs of fighting can be huge) so once the initial battle has taken place to establish where the boundary should be, scent marking offers a conflict-free method of letting each other know that you’re still around. Less time spent fighting also means that more energy can be devoted to finding food.

In a paper to the Canadian Journal of Zoology during 2011, Janosch Arnold, Carl Soulsbury and Stephen Harris report that foxes change their behaviour when unfamiliar urine is encountered in their territory. The researchers applied artificial fox urine to known fox territories to simulate the presence of an intruder and radio-tracked the residents to see what they did. The dog foxes didn’t change the size of their territory, or the amount of time they spent active. The dogs did, however, shift their daily activity range so they spent more time in the area where the fake scent had been applied; this was more pronounced in big males than smaller ones. The foxes searched a greater proportion of their territories on nights after the scent was applied than before the scent arrived – presumably looking for the intruder. Vixens showed no significant change in either their searching behaviour or activity range, suggesting that territorial defence is more male-centric. See Q/A for more details on this study and, more generally, how foxes use scent to communicate.

Territory borders may be recognised by the presence of alien urine or, perhaps equally as probable, the presence of a familiar urine that the resident associates with a neighbour. In a recent note to BBC Wildlife Magazine, Stephen Harris noted how, when the foxes and badgers first appear in his garden in the summer, they sniff each other carefully and then ignore one another, but get very agitated when a stranger turns up. This, and many similar observations from other researchers, suggests that foxes are capable of recognising familiar and unfamiliar animals and that neighbouring territory holders may thus be able to recognise each other. Indeed, during the mid-1970s University of Washington psychologist David Barash trapped seven foxes and held them in cages so he could observe their reaction to each other. Barash found that foxes trapped near each other (within 8 km / 5.5 mi) showed dominance-submissive behaviour towards each other, while those trapped further apart showed more aggressive behaviour (threat gapes) to each other. Despite the small sample size, Barash's data suggest that foxes can recognise their neighbours and that there may even be a rudimentary social structure between them. This is perhaps not surprising as, in urban areas at least, neighbouring groups are often related. Whether or not an intruding fox recognises the resident, several authors have described how invading individuals change their behaviour when they enter another fox’s territory, moving more erratically and ceasing all scent marking. In 1972, the late-great zoologist Niko Tinbergen described how territory holding foxes on the sand dunes of the Ravenglass-Drigg Sanctuary in Cumberland knew their ranges very well and always used the same tracks (often in almost straight lines across open sand) from their earths to favoured hunting grounds; he sometimes found what amounted to ‘fox highways’ along the shoreline. Newcomers to the area, Tinbergen noticed, acted quite differently:

A fox entering a strange hunting ground changed its behaviour: instead of running in a straight line across the open sands it would try to keep under cover and would move hesitatingly and follow an irregular route.”

Not only do foxes know what area their own territory covers and when they’re trespassing in someone else’s domain, there are some data suggesting that they know where their territories are even if they’re picked up and dumped somewhere else – in other words, that foxes have a homing ability. In Minnesota, USA, for example, wildlife biologists Robert Philips and David Mech found that a vixen they captured, translocated and released in November 1968 travelled the 56 km (35 miles) back to her original capture site within 12 days. Quite how this vixen knew where her territory was remains a mystery, although it has been shown that European badgers (Meles meles) have a good idea where their territory is relative to those of their neighbours and can use this knowledge to find their way home; foxes may retain the same information.

So we’ve seen how big a territory can be and how foxes mark it out, but how much of its territory does a fox use? This, like everything else we’ve tackled in this section, is not an easy question to answer either! There are many factors that influence how much of a territory gets used and how far a fox will travel each night, although the impact of season is perhaps most significant. The vast majority of tracking studies show the same trend: during the breeding season (winter) foxes travel further than they do at other times of the year. Indeed, during the breeding season males are known to move over large areas -- regularly trespassing -- as they search for receptive vixens, while females typically spend a greater proportion of the time at the periphery of their territories (again, this probably facilitates mate-finding). Studies in North America have found dogs increasing the length of their nightly movements by four to eight times come the breeding season. Similarly, tracking of Bristol’s foxes has found that average winter ranges of males were more than twice the size of those in spring, summer and autumn (although caution should be used owing to low sample size) as they trespassed into neighbouring ranges in search of receptive females with which to mate – there was no significant difference in the seasonal range of females. Interestingly, although no seasonal difference was found for females in Bristol, this may indicate that none became pregnant during the study. Several studies have demonstrated how pregnant foxes move shorter distances around the time they give birth and for several days after the cubs are born. Working with the foxes of the Ashio Mountains in Central Japan, for example, Masahiko Takeuchi and Masaaki Koganezawa found that their pregnant vixen’s range had decreased by six-fold by the time her cubs were about to be born (pre-breeding range was 601 ha, declining with the advance of her pregnancy to 109 ha by the time her cubs were born).

Red fox restingSeasonal variations in ranging may, however, be for reasons more subtle than searching for a mate or the birth of cubs. Studies in Europe have shown that, during the late summer and autumn, foxes feed heavily on fruits that are locally clumped (they can strip a bramble bush of blackberries in no time); the result is that they need to move around less than they do during the summer or winter (when finding food for cubs and when food is more difficult to find, respectively). Generally speaking, foxes move roughly the same distance each night, although adverse weather conditions (especially snow cover) may reduce the distance travelled. In Bristol, foxes moved an average of eight kilometres (5 mi.) per night, rarely exceeding 10 km (6 mi.). Similar values have been recorded in Japan (6-8 km) and Spain (4 – 5.5 km / up to 4 mi.), with slightly longer trips (up to 15 km / 9 mi.) in more remote European and North American environments. In the UK, the longest distance travelled by a fox that I have come across in the literature was a male that was tagged as a cub by Huw Lloyd at an earth in mid-Wales and was later shot by a gamekeeper 52 km (32 miles) to the north-east. More recently, however, Brighton University's Dr Dawn Scott tagged an adult male fox in suburban Brighton that was tracked a staggering 315 km (195 miles) from Brighton to Rye in East Sussex in just under one month. This particular fox, known to BBC Winterwatch viewers as Fleet, was believed to have been ousted from his territory by his son (possibly as a result of his suspected lungworm infection); he left Brighton on 9th December 2013 and in two days had reached the rural setting of Ditchling Beacon on the South Downs, some 7 km (just over 4 miles) away. The fox spent a couple of days on the South Downs Way before heading north-east, through various towns and villages and, by 18th December, he had travelled some 200 km (124 mi) from his previous territory. Fleet moved south briefly, towards the A27, and then back north to spend Christmas Eve and Christmas Day at a caravan park near Uckfield, where he was presumably fed by, or scavenging food from, residents. The track continued to just north of Westfield in East Sussex, where the signal was lost during early January 2014; a total distance of 315 km and by far the longest verified dispersal by a single fox in Britain. Moreover, Fleet's impressive ramble is not far off the current record for Red fox movement, which is held by a dog fox tagged in Wisconsin and recaptured nine months later 394 km (246 miles) in Indiana. It should be noted that, despite a fairly extensive search of the area where the final signal was received, there was no sign of Fleet's body, suggesting that the collar may have failed, and Fleet's journey may still be in progress.

Foxes may temporarily leave their territory if there are highly concentrated food resources nearby. Foxes in Japan’s Shiretoko National Park, for example, were observed to leave their territories for up to three days while they foraged on concentrated food sources (salmon carcasses and human food) elsewhere in the park, although they didn’t stray more than eight kilometres outside of their range. Overall, it seems that foxes focus most of their time at specific parts of their range (generally feeding and resting spots), so they may move several kilometres, but stay in a relatively small area, often using only part of their range. When foxes do move around during their nightly activities they do so along a series of well-defined paths that are about 30 cm (12 in.) in diameter and on which the grass has a ‘trodden down’ appearance. Commonly foxes will use the same paths on successive nights if they lead to a favoured hunting spot, although my experience is that they are less predictable in their habits than badgers. Foxes often opt for the path of least resistance while commuting, using field margins, badger or deer runs, or the ‘tramlines’ of vehicles that have driven across the field.

It is sometimes assumed that, as part of its nightly wanders, a fox will travel in a circuit around the territory, essentially patrolling the borders. In some cases (where territories are small and the fox density is high) this invariably does happen, but many studies have found that foxes focus the majority of their activity in a core area (a breeding earth or rich hunting ground, for example). Studies both here and in the USA have found that, in most cases, foxes don’t visit their territory borders every night; in a large territory the fox may only visit a border area once every few days, although the movements of adult members of a group appear to collectively result in visits to all borders every week-or-two. Even in small ranges, the fox invariably doesn’t use the entire range every night. Indeed, in 2002, Polish biologist Jacek Goszczynski reviewed the published data on fox home range and found that foxes living in small ranges (up to 150 ha) used 36-70% of the range daily, while those living on larger ranges travelled over similar sized areas but that these represented a much smaller proportion of the seasonal range (only 16% of the largest home range included in the analysis was used on any single day). So, the foxes moved over roughly the same sized area each night, regardless of how large their territory was, even if that meant some areas were almost never visited.

It should be noted that, although territoriality is well known in Red foxes throughout most of their range, it is not observed in every population. Between January 1989 and April 1992 (with an intermission during the Gulf War), a team of biologists from Oxford’s Wildlife Conservation Research Unit led by David Macdonald conducted a detailed study on the Red foxes of the biological reserve of Thumamah in the great sand deserts of Saudi Arabia (Vulpes vulpes arabica). Over a period of three years, 41 foxes (21 males and 20 females) were fitted with radio collars and their movements tracked, revealing an average home range of 676 ha (almost 7 sq-km or just over 2.5 sq-mi) that didn't vary according to sex or season. The most interesting discovery was the lack of territoriality; instead they observed loose-knit groupings, with females sharing territory more readily than males. The biologists suggested that this situation arose because it helped the foxes, which are smaller than Red foxes found in Europe (i.e. about half the size of those in the UK), survive in an extremely harsh environment with a spatially and temporally sparse food supply.

Finally, it is worth mentioning that, even where territoriality is commonplace, not all foxes partake. Indeed, it is estimated that some 15% of adult Red foxes wander with no fixed home range; these animals are called itinerants. Little is known about the behaviour of itinerant foxes, although studies by Andrew Wilson during the mid-1990s suggest that these animals behave differently to territory holders in their habitat use. In his bio of the Red fox in the RSPCA’s 1981 British Mammals book, David Macdonald notes that itinerants are usually males and may move in a straight line or weave a meandering course through the countryside, ranging up to 250 km (170 mi.); he gave average ranges of 20–50 km (13.5–34 mi.) for males and 7-15 km (5–11.5 mi.) for females. Macdonald does point out that the distinction between itinerants and residents is blurred, with some territory holders commuting long distances between centres of activity. Indeed, in a contribution to a 1980 special edition of the journal Biogeographica on Red fox ecology, Huw Gwyn Lloyd noted that, although it’s often perceived that foxes are either sedentary or itinerant, in reality an individual can be intermittently itinerant; in mid-Wales he tracked a dog fox making frequent excursions out of his territory (up to 16 km away), but always returning to his familiar range sooner or later. It has also been established that if a juvenile fails to establish a territory, its activity area becomes smaller and it becomes what German biologist Ad Vos called a “floater” (local itinerant) in a 2003 paper to the Journal of Veterinary Medicine; these animals generally occupy border zones between neighbouring territories. (Back to Menu)

Golden eagle eating foxPredators: The concept of what exactly makes a predator is far from straightforward. Often, a predator is thought of as anything that kills something else, but the zoological definition of a predator is an organism (typically, but not exclusively an animal) that catches, kills and eats another animal – these three components are important. This definition works well for most of the species we typically think of as predators -- lions, tigers, most sharks, crocodiles, birds of prey, wolves, etc. -- and may also include many herbivores (if they find, up-root and eat a plant), although there are some grey areas: where things like Cookiecutter sharks (Isistius brasiliensis), which catch and feed on prey but don’t kill it, fit in, for example. The important point, however, is that a predator hunts other animals (arguably also plants) for food. This is different to one animal killing another while fighting over a mate, or killing another animal to stop it eating your food, drinking your water, using your space, etc. The reason I’m labouring the point somewhat is that in most cases where foxes are killed by other large predators (wolves, coyotes, lynx, bears, dingoes, etc.), it is invariably done to remove a potential competitor. Coyotes and foxes, for example, feed on the same types of small mammal prey and so the former frequently kill the latter to remove the competition – this is referred to as competitive exclusion. The coyotes very rarely (if ever) eat the foxes they kill; they don’t see the foxes as prey, they see them as competition to be removed, so they are not technically predators of foxes. The same is true of domestic dogs, which occasionally kill foxes but do not consume the carcass. Indeed, foxes have very few true predators; indeed, more generally, predators rarely eat other predators.

The threats posed to foxes by other large carnivores (wolves, lynx, bears, dingoes and coyotes, all of which can potentially have a significant impact on fox numbers) through competitive exclusion is covered at length in an associated Q/A and will not be duplicated here. Sufficed to say, foxes can be displaced by these larger carnivores (e.g. wolves, coyotes, bears) and the relationships may be complex. In a recent paper to the journal Ecology, for example, Taal Levi and Chris Wilmers at the University of California report how the reintroduction of wolves causes the displacement of coyotes and an increase in fox abundance, which potentially has consequences for local small mammal and bird populations.  Despite such ecological 'cascades', with the possible exception of lynx, none of these are true predators of foxes. There are, however, some animals for whom foxes -- especially cubs -- are very much on the menu. A recent (2007) study published in the Journal of Wildlife Management estimated that 38% of Red foxes in rural areas of the USA died following predation/aggression from coyotes, compared with only 12% living in urban areas. Domestic dogs may also suppress fox populations through both direct attacks (particularly on cubs) and disturbance and it has been suggested both that high numbers of feral and stray dogs in developing countries may explain the apparent lack of foxes there and that recent control of stray dogs in Britain has made life a little easier for urban foxes.

In the UK and much of Europe the main non-human predator of the Red fox is the Golden eagle (Aquila chrysaetos - above). In the UK, this magnificent raptor is restricted to the Highlands of Scotland and isolated patches of northern England (e.g. Cumbria), while globally it ranges over most of the Northern Hemisphere, from the southern border of the Arctic Circle south to roughly the Tropic of Cancer. According to the Royal Society for the Protection of Birds, Golden eagles can lift a maximum of four or five kilograms (9–11 lbs) – adult male foxes average around 7 kg (15.5 lbs), while females average 5.5 kg (12 lbs), which might suggest that only young foxes are taken by these raptors. That said, adult eagles may kill adult foxes and feed on the carcass in situ, rather than carrying the carcass away. Cubs are, nonetheless, the most common victims and, in his 2010 opus The Golden Eagle, the late eagle ecologist Jeff Watson noted that it is not unusual to find the remains of fox cubs in eyries (eagle nests), especially in the western Highlands of Scotland. Similarly, in her 2001 book The Blood is Wild, Bridget MacCaskill noted how, upon climbing to an eyrie in the Scottish Highlands, she and her husband found:

At the back of the nest, where ledge met sheer cliff, lay two crumpled bundles of red fur. Two small brushes, both with a white tip, were still attached.

Watson gives values of canids (mainly Red foxes, although domestic dogs are occasionally taken) in the diet of UK eagles ranging from 0.6% in the eastern Highlands of Scotland to 4.3% in the south-west Highlands and describes how the birds use a “low flight with slow descent attack” (one of seven attack strategies) to hunt carnivores. This strategy involves hovering motionless over prey and, when the prey turns its head away, the eagle swoops down, lands on the back of the neck and ‘rides’ the quarry until it collapses; the prey is held by the eagle until it’s dead.

European Eagle owlStudies elsewhere on Golden eagle diets have revealed similar data to those given by Watson – that foxes are not an uncommon dietary component, but generally don’t represent a significant part of the diet. During a five year study of eagle diet in Sweden, Martin Tjernberg found Red fox remains in 47 (1.6%) of the 2881 items recovered from 162 eyries. Splitting these data out, Tjernberg found that foxes accounted for less than 1% of the diet of eagles living in mountainous regions, 1.5% of those living on mountain slopes and almost 2% of those living in coniferous forests. Of these fox remains, the vast majority (83%) were cubs. A study on Golden eagle diet in the central-eastern Italian Alps between 1984 and 1989 found that foxes contributed 4% of the diet while, in a 2001 paper to the journal Ardea, a team of French biologists presented figures showing the abundance of canids (again, presumably largely Red fox, although the authors don’t specify) in the diet of eagles in the Mediterranean Basin; dietary occurrence ranged from 0.7% in the southern Alps to just over 13% in Sicily. Why, though, should there be such variation in the contribution of foxes in the diet of eagles? The answer, it seems, may lie in the availability of the eagles’ preferred food. In a fascinating literature review of superpredation (where one predator kills and eats another) in four large European birds of prey (Goshawk, Golden eagle, Bonelli’s eagle, and the European Eagle owl), a team of Mediterranean biologists argue that the food stress hypothesis explains why these birds take carnivores. Essentially, the authors suggest that when the eagle’s preferred prey (e.g. deer, rabbits, hares, game birds, etc.) is in short supply, they are forced to broaden their diet to include prey they wouldn’t normally bother with; predators are, after all, more difficult to find (they exist in lower numbers) and more dangerous to catch than their normal prey animals. The fact that cubs tend to appear on eyries (when adults have hungry chicks to feed) seems to support this theory. This literature review reports that all the papers they found on Golden eagle diets had some mention of fox, but they made up only just over 2% of the combined diets; foxes were found among prey remains of the Bonelli’s eagle (Aquila fasciata) and Eagle owl (Bubo bubo - left), but made up less than 0.5% of the diet of each.

So, overall Red foxes don’t seem to be a significant food source for Golden eagles, but there are examples where these birds have caused considerable declines in other fox populations. The situation is quite different for the second smallest fox species -- the critically endangered Island fox (Urocyon littoralis) -- on the California Channel Islands. It seems that a major decline in the population of feral pigs caused the eagles on the islands of Santa Cruz, San Miguel and Santa Rosa to switch their diet to focus more heavily on the islands’ foxes, causing a catastrophic (95%) decline in the populations – such was the concern that the Island Fox Conservation Working Group (IFCWG) was established in 1999 to address the issue. The IFCWG set about catching as many of the foxes as they could and holding them in captivity while they began re-locating the eagles away from the islands. In a paper to the Proceedings of the Sixth California Islands Symposium, Brian Latta and his colleagues report that, as of August 2003, they had removed 70% of the known eagles from Santa Cruz and Santa Rosa, which has led to fox survival on the former island having risen to near pre-decline levels. Tracking of the eagles suggests that, once re-located to north-eastern California, the birds survive and don’t come back to the islands; translocation thus appears to be a viable alternative to lethal control. How this scheme will pan out in the future, with new birds migrating in as the regional population grows, remains to be seen.

The only other bird of prey in Britain capable of taking foxes is the European Eagle owl (Bubo bubo). It is widely cited that Eagle owls will take foxes, both adults and cubs, although there is a scarcity of data to show how significant they are as a predator. In the aforementioned literature review of raptor superpredation, fox remains were identified in just under half the dietary studies of Eagle owls, accounting for only 0.3% of the total diet. There are some reports to suggest that foxes may not be favoured prey, being ‘picked at’ by the owls, rather than consumed greedily. One such account is of an owl that was found to have cached a fox cub, which it consumed over several days. In his 1983 Owls of Europe, Hemio Mikkola described how, one evening, a female Eagle owl was seen to:

“…remove an entire fox cub from beneath a neighbouring plant Smilax, having concealed the cub the day before or that same morning. The fox was not completely eaten that night and its remains were hidden again in the same place at the end of the meal. The next day, the operation was repeated.”

Other occasional predators of Red foxes include Long-tailed weasels (Mustela frenata), ermine (Mustela erminea), skunks (Mephitis mephitis), mink (Mustela vison) and snakes, all of which may take young fox cubs. In North America, as in Europe, owls (Strigiformes) and hawks (Accipitriformes) take older cubs and occasionally adults.  Even smaller birds will sometimes attack foxes, although it seems unlikely that they see them as prey. There was a fascinating account in a 1964 issue of British Birds describing an apparently unprovoked attack by a Tawny owl (Strix aluco) on a Red fox drinking from a pond in the owl's territory one day in January.  It’s unclear why the owl launched the attack; it seems very unlikely the fox posed it any threat and it is too early in the year to be protecting a nest (although there is a reliable report of a Tawny owl chick in mid January in south Wales).

Arguably humans can also be considered a predator. Fox meat can be purchased at some butchers in the UK and, in at least one location in Asia, humans have teamed up with Golden eagles to hunt foxes for meat and skins. This fascinating partnership was recently filmed by the BBC for inclusion in their Human Planet series. The wide-open terrain of the Altai Mountains in Western Mongolia makes hunting almost impossible and this has led the Kazakh people, who have inhabited these mountains for some 200 years, to form a unique relationship with the resident Golden eagles. The hunters capture a chick from the nest and train it (for about five months) to hunt; they then head out on horseback, carrying the eagle, to hunt Mongolian Red foxes (Vulpes vulpes beringiana) on the snowy tundra. The hunters take the eagle to high ground, from where it may observe fox movement on the tundra below and take off in pursuit. The fox clearly recognises the eagle as a predator and runs for its life; at some point during the chase, however, the fox turns and faces down the eagle, growling and gekkering. It seems that if the eagle does not hit the fox directly (landing instead on the ground next to the fox), the prey escapes. If, however, the eagle can land on the fox, the bird’s job appears to be to pin the fox down until the hunter arrives to dispatch the prey – it’s not clear how proficient the eagles would be at killing these adult foxes themselves. The eagle is then given the fox’s lungs in reward while the meat and fur is used by the tribe. Not all eagles, it seems, can be trained to hunt foxes.

Red deer hind suckling calfWhile not technically predators, foxes have been intentionally killed by deer, typically when perceived as a threat to their young. The great writer and naturalist H. Mortimer Batten, in a comment on a statement by eminent Highland ecologist Frank Fraser Darling that foxes regularly killed Red deer (Cervus elaphus) calves, described how a group of Red deer hinds (females) surrounded a fox hiding in a clump of bracken, walked slowly inwards and “trampled that fox into a jelly”!  Foxes, especially their cubs, may occasionally fall foul of European badgers (Meles meles) too. As with deer, badgers typically aren’t true predators of foxes (for the same reason that wolves, coyotes, etc. aren’t), although they may have a significant impact on their population, and some of the data from the Randomised Badger Culling Trial in England suggest that reducing badger numbers can lead to an increase in foxes through competitive release (remove your competitor and there’s more room for you to thrive). This finding warrants further study, but it certainly seems plausible that reducing badger numbers provides plenty of free setts (which foxes will also use) and frees up food that the two species normally compete for (e.g. earthworms, rabbits, fruit, etc.). While the precise impacts require further study, we do know that aggression is at least one mechanism by which badgers displace foxes.

In North Wales during 1958, Abel James witnessed a stand-off between a vixen and a badger on a cliff edge. Mr James noted that the fox and badger were snarling at each other when the vixen, finding herself trapped, tried to leap over her opponent. Unfortunately for the vixen, the badger reared up and seized her leg and the two proceeded to roll around the cliff top locked in combat. The pair rolled towards, and then over, the cliff edge – by the time Mr James made it down the cliff, both were dead. Mr James’ account is not unique and, in their book Badgers, Ernest Neal and Chris Cheeseman describe several instances of badgers and foxes embroiled in fierce combat. Similarly, in his 1923 book, The Badger Afield and Underground, Batten provides several examples of badgers killing fox cubs. Perhaps the most interesting account, however, comes from E. Clay in a communication to The Countryman. Mr Clay described hearing screams coming from a dense blackberry bush while watching fox cubs play on a hillside near his home in Devon. Upon moving closer, he discovered one of the fox cubs lying there with one of its back feet bitten off, its hind quarters apparently paralysed and skin torn on its shoulders. Mr Clay then saw the head and forequarters of a large badger appear; it gripped the cub by the throat and dragged it down a nearby hole. This account is interesting because it bears considerable resemblance to a feeding-motivated attack, rather than a defensive strike. Obviously Mr Clay was unable to follow the badger down the hole and it remains unknown whether the fox cub was consumed. It should be noted that incidences of badgers killing foxes (and indeed, foxes killing badgers) are far from commonplace, and where the two species occur together they are usually very tolerant of each other, although it is the badger that is invariably dominant.

Finally, foxes may be predated by other foxes. The subject of infanticide (the killing of young) in Red foxes, the carcasses of which are occasionally eaten, is covered in an associated Q/A, and there is plenty of evidence that adult foxes will sometimes kill other adults. There is also evidence to suggest that foxes will scavenge fox carcasses if they happen upon them (I know of no reports to suggest they deliberately kill and eat other adult foxes). Indeed, in a 2010 paper to the journal Contemporary Problems of Ecology, Russian researchers noted that, under adverse conditions, foxes engage in cannibalism. One of the report’s authors, Tatiana Kiener at the Moscow State University, told me of the following incident at the Sikhote-Alin Nature Reserve in the Russian Far East during March 2008:

A red fox corpse (male) was found near a waterstream in snow. It was about 1 week old. We observed some old traces – a kind of struggle in snow. There were also the tracks of the other fox (male) on the snow. The other fox visited the corpse several (5-6) times. All meat was devoured. There were no tracks of other animals nearby. We suppose it could happen under deficit of food in this season.”

Urban foxes are occasionally found with fox remains in their stomachs (see: Food and Feeding); these are presumably scavenged from road-kill, but imply that cannibalism may not be restricted to very harsh environments. (Back to Menu)

Red Fox with Food at SunsetFood and Feeding: Essentially, foxes are small and medium-sized mammal (particularly rodents and lagomorphs) specialists; that is, they evolved to feed primarily on mice, rats, voles, rabbits, etc. This does not, however, mean that foxes only eat rodents – nothing could be further from the truth. Indeed, the problem when it comes to describing what’s on the menu is that the Red fox, as a species, has an almost unimaginably catholic diet. As a general rule of thumb, foxes are local opportunists – in other words, they take whatever prey is abundant (locally and seasonally) at the time. A consequence of this unspecialised selection is that foxes can live almost anywhere and eat almost anything, switching prey as necessary; at the same time, however, it means that the diet varies with habitat, season, and individual preference, which makes it extraordinarily difficult to generalise. With that in mind, the following is not intended as a complete list of prey species, or a comprehensive review of the literature (many have written theses on that subject!), but rather a summary of the diet and feeding behaviour of the Red fox.

Foxes, along with all dogs, are classified within the taxonomic order Carnivora, from the Latin meaning ‘to devour flesh’. This taxonomy is slightly misleading because there are meat eaters that aren’t included in it and, at the same time, some animals are included that eat very little meat (only about 36% of the Carnivora have a diet consisting of at least 60% meat). Consequently, animals that actively include meat in their diet (as opposed to those that may take meat very occasionally or incidentally while feeding on other things) are called carnivorans. Carnivorans can be broadly split into two groups: those that depend on meat for their survival (the obligate carnivorans) and those that eat meat when available but also eat (and can survive on) other food sources (the facultative carnivorans). We won’t concern ourselves with it here, but some biologists go further, dividing carnivorans into hypercarnivores (diet with 70% or more meat), mesocarnivores (50-70%) and hypocarnivores (30% or less). Foxes fall into the facultative carnivoran group – taking animal prey as the opportunity arises, but also eating other foods, including plants, fruits, fungi and garbage. That said, Red foxes are carnivorous first and foremost and a study by Carolyn Jaslow at the University of Chicago in 1987 found that foxes were more efficient at digesting mice than they were fruit (89% vs. 51% efficient), suggesting an adaptation to a more carnivorous than omnivorous diet.

It sounds like a rather obvious statement, but food is a critically important resource for a fox – it’s worth fighting over, it plays a role in determining how big a territory is and thus how many foxes can live in an area, and influences when a fox breeds. Indeed, in a study on the timing of Red fox reproduction, published in 1995, biologists at the University of Siena in Italy found a general trend for foxes living at higher latitudes to ovulate later than more southerly animals (see: Breeding Biology). This, the biologists suggest, reflects the reduced food availability in the north during winter. Given how important food is as a resource, it is not surprising that much research has gone into establishing what foxes eat, with many hundreds of studies having been published worldwide. I will provide some examples of diets from selected areas in order to give an idea of the variability, but it is worth remembering that there are some inherent biases in the analysis of fox (indeed any animal) diet.

Firstly, we have the issue that foxes scavenge, which means that simply finding remains of a certain species doesn’t necessarily imply predation (finding cat or sheep remains in fox scat, for example, doesn’t necessarily mean that the fox killed the animal). Secondly, some components are more resistant to digestion than others and some may be unrecognisable or barely detectable by the time they leave the body in scat (fat and muscle tissue stripped from a carcass, for example). Consequently, it is not unusual for different dietary studies to yield different results, especially when using different sources (stomach contents, intestine contents, or scat contents). A 1995 study by Paolo Cavallini and Teresa Volpi, for example, found that studies based on stomach contents recorded twice as many bird remains as those based on scat analyses, while an earlier study calculated that only just under half of small rodent teeth made it into the scat. Thirdly, is the format in which the results are presented. Frequently the data will be graphically displayed as a pie chart showing the percentage of the diet each animal or group constitutes. These data are typically collected from scat and/or stomach analysis and may show, for example, that 70% of the scats or stomachs contained rabbit remains. This tells us that most of the foxes in the study area were feeding on rabbits, but it doesn’t tell us how important rabbits are to the fox. So, although most foxes had rabbit remains in their stomachs/scats, each could have had the remains of only a single rabbit – at the same time, 50% may have had 10-or-more voles in their stomach. Our pie chart would show rabbits as a bigger dietary component -- and imply they were a more significant prey item -- simply because more scats/stomachs contained them, even though voles are (when you correct for weight) a more important prey item. The point is that a degree of caution should be used when interpreting any dietary studies; they may not tell the whole story.

Red fox scatRed fox scat
Fox scat (indeed, faeces in general) vary in their appearance and consistency according to what the animal has been eating. A glut of earthworms can give the scat a jelly-like appearance, while fruit can give it a dark colour and see it full of seeds (above, left), and a largely mammal-based diet produces drier scats that are predominantly teeth, claws and fur (above, right).

For those interested in the more physiological side of feeding, in a 1980 paper to Biogeographica, Darrell Sequeira summarised the studies of gut residence times in foxes. It seems that about 90% of a fox’s meal passes out within 48 hours (most within just over a day) and a fox defecates, on average, about five times per day. One study, published during 1955, gave some more detailed residence times: eight hours for mice; six hours for ‘other meat foods’; four hours for insects; and two hours for plant material. In his 1980 book The Red Fox, Huw Lloyd noted that food starts passing from the stomach -- which can hold up to about a kilogram (2 lb. 3 oz.) of food and distend to around 900 mL (about 1.5 pints) -- into the large intestine after about two hours; this is apparently a gradual process and it may be several hours before the stomach is empty. According to Lloyd, food remains start appearing in the faeces five-to-ten hours after being eaten, but remnants may still be found in the intestines up to 24 hours after the meal. Being a carnivore, the Red fox has a short gut, with a small intestine of about 110 cm (3 ft 7 in.) long and a large intesting about 50 cm (20 in.) long; the caecum (the first part of the large intestine attaching to the appendix and involved in the digestion of plant material) is essentially vestigial. Jan Englund’s data on captive silver foxes suggest the second meal of the day passes more slowly than the first. Fox faeces (above) are usually about two centimetres (three-quarters of an inch) thick and three-to-nine centimetres (1 – 3.5 in.) long; they’re expelled covered in a film of mucous, which probably helps protect the delicate tissues of the lower gut from sharp bones, teeth and claws in the prey remains. At the other end of the animal, the typical fox dental formula is 3/3 (incisors): 1/1 (canines): 4/4 (premolars): 2/3 (molars). The formula presents the number of teeth in the top and bottom (as top/bottom) of one side of the jaws – Red foxes have 42 teeth.

So, if food is such an important resource, how much time do foxes spend looking for it and what do they look for? The average adult fox requires between 350g and 550g (12 – 19 oz.) of food per day and the amount of time and effort devoted to sourcing food varies terrifically, both individually and according to season. During the cub-rearing season (late spring and early summer) the adults will spend most of their time searching for food for their rapidly growing offspring. At other times of the year, it seems that foxes spend about one-third of their waking time looking for food. Indeed, the foxes studied by J David Henry in the boreal forests of northern Canada spent some 35% of their day (about 5 hours) searching for food. In terms of the number of different things a fox will eat, I suspect one could fill an entire book with them all – I don’t intend to try! One study of foxes in Missouri, for example, recorded 34 different mammal species, 14 species of bird, 15 families of insects and 21 species of plants in the diet. Indeed, Mark Cardwine, in his 2007 Guinness Book of Animal Records, considered that, by a small margin (the Grey wolf, Canis lupus, being a very close second) the Red fox had the greatest dietary breadth of any member of the dog family. Below are some examples of fox diets (Click to Enlarge). (Back to Menu)

Red Fox Diets
Examples of the diets of the Red fox in various habitats. Click to enlarge and for more details.

Types of prey consumed
Bank VoleSuffice to say, foxes are extraordinarily opportunistic, omnivorous predators. Nonetheless, most studies agree that they feed predominantly on small mammals, particularly rodents (rats, mice, voles and the occasional squirrel) and lagomorphs (rabbits and hares); in rural areas these groups together typically account for about 50% of the diet. Bank voles (Myodes glareolus - left) and Field (or Short-tailed) voles (Microtus agrestis) are the most numerous of the small mammals taken, although mice and rats often appear on the menu, especially in urban areas. During his studies with his captive vixen, David Macdonald found that she showed a clear preference for Field voles over both Bank voles and Wood mice (Apodemus sylvaticus). Roger Burrows found the same preference in his local foxes; they ate Field voles most often, with Bank voles, Wood mice, Brown rats (Rattus norvegicus), and Grey squirrels (Sciurus carolinensis) taken on occasion. Wild rodents taken elsewhere include hamsters (Cricetinae), gerbils (Gerbillinae), Ground squirrels, Pocket gophers (Geomyidae), Deer mice (Peromyscus spp.) and Groundhog (Marmota monax). Shrews (Sorcidae) are often caught, and sometimes cached, but rarely eaten, presumably because they are distasteful. Scent glands on the flanks of shrews produce an oily secretion with a strong-smelling ‘musty’ odour, which is used in scent-marking and communication and probably makes them unpalatable to many predators. Moles (Talpa europaea) also excrete a musky-odoured secretion from scent glands on their stomach – again, like shrews, this is probably distasteful to predators and explains why, although moles are sometimes caught by foxes, they’re seldom consumed. Indeed, Lloyd presented four captive fox cubs with a mole each and observed how:

Three of the cubs promptly buried the moles and the fourth one ate one foreleg and shoulder, which it vomited a few minutes later.

David Macdonald, in a 1977 paper to Mammal Review, concluded that insectivores such as shrews and moles were only eaten when other, more preferable, foods were scarce. In most cases, moles and shrews are probably unintentional victims of the fox’s hunting method (see below), which essentially means the fox doesn’t know what it is hunting until it has caught it.

Hedgehog (Erinaceus europaeus) remains occasionally turn up in fox scat and there is much debate about how significant foxes are as a predator of these spiny mammals (see: Q/A). There are many stories telling of the various methods that foxes apparently have to get a hedgehog to uncurl (including urinating on it or rolling it into water), but they’re rarely witnessed. That said, I have come across a couple of reliable accounts of foxes urinating on hedgehogs, although it remains unknown whether it was to get the animal to uncurl, or just part of their predilection for scent-marking conspicuous objects in their territory. In neither case did the hedgehog unroll. Recently, however, there have been concerns raised on discussion lists that foxes are a significant force in the decline of hedgehogs. Unquestionably, foxes can kill hedgehogs. The problem is that nobody knows how commonly this occurs and there is currently no evidence, that I know of, to support such inferences, although in Urban Foxes, Stephen Harris and Phil Baker noted that there was an increase in Bristol's hedgehog population following the outbreak of mange (which drastically reduced fox numbers) in the mid-1990s. We don’t know, however, whether this was a reduction in predation or an increase in food (foxes and hedgehogs both feed heavily on worms and insects), or both. There are certainly some reports of foxes feeding heavily on hedgehogs when times are tough. In their Mammals of the Soviet Union, Vladimir Heptner and Nikolaï Naoumov described the diet of foxes living in central forest districts of the Soviet Union during a vole population crash in the mid-1930s:

In these years, the stomachs of foxes were at times completely full of hedgehog remains, swallowed along with the skin as well as quills of these animals, which protruded into all sides, bulging out from beneath the thin wall of the stomach.”

Another study, this time in South Devon found that hedgehogs once again formed a notable component of the diet during harsh weather. In his study of the diet of foxes living on Higher Well Farm between March 1974 and August 1975, D.F. Richards found that hedgehog remains appeared more often in winter than other seasons and, in a 1977 paper to the Journal of Zoology, he wrote:

The most frequent occurrence of hedgehogs in the present survey was in Winter, when remains were found in 13% of scats, and these animals may well have been dug out of hibernacula.

Generally-speaking, however, hedgehogs don’t appear to contribute a substantial amount to the diet, being either absent from most studies or rarely representing more than a couple of percent of the total food. Moreover, it is likely that many occurrences of hedgehog remains represent scavenging of road-kill.

Fox cub and hedgehogHedgehog remains
Foxes do sometimes prey on hedgehogs, although the data we have suggests that such behaviour is not common. Hedgehog remains are fairly common in fox scat, although it is unknown whether these hedgehogs were predated (i.e. killed and eaten by the fox), or were killed in other ways (e.g. run over) and scavenged by the fox. Foxes tend to bite the spines off, leaving clumps of spines and skin (above, right), while badgers effectively skin the animal, leaving a complete jacket of spines. My experience is that foxes tend to be curious of hedgehogs (such as the cub in the photo above), although I have little doubt some individuals could learn to predate them.

Other mammal remains occasionally reported in Red fox diets include otter (Lutra lutra), stoat (Mustela erminea), weasel (Mustela nivalis), Red deer (Cervus elaphus), Roe deer (Capreolus capreolus - particularly kids), European badger (Meles meles), opossum (Didelphidae), raccoon (Procyon lotor), porcupine (Hystricomorpha) and wild boar (Sus scrofa). In a study of fox diet on moorland in Hungary, Jozef Lanszki found wild boar (adult and piglet) remains in 18 (23%) of the 77 scats he dissected. Fox remains also turn up occasionally, suggesting cannibalism, although this is presumably scavenging or infanticide (see Q/A and below). The remains of kangaroos are sometimes found in the faeces of foxes from Australia. A study published in 1971 found that Red kangaroos (Macropus rufus) shot and left by hunters were an important food source for foxes living in arid New South Wales, while another study (published in 1973) in Victoria found Grey kangaroo (M. giganteus) remains, again presumed scavenge, in fewer than 1% of the scats analysed. In Australia, where foxes are an invasive species, they can have a significant impact on endemic mammal species (see: Interaction with other Species). Finally, there is one confirmed report that I am aware of recording human flesh in the stomach of a fox. A study of almost 2,000 fox scats from Sherbrooke Forest Park in south-eastern Australia by Hans Brunner, John Lloyd and Brian Coman found human remains in one scat – it turned out that the fox had scavenged the corpse of a suicide victim. There are a few reports of foxes disrupting the burial places of people in both urban and rural Britain; particularly the ‘pauper graves’ of children, which are often coffins made of cardboard that quickly degrade in the soil. Indeed, Wandsworth council in London were prompted to review their policy of pauper graves after a fox excavated the body of a dead baby in September 2009. It should be noted that, while such events are distasteful to most of us (and traumatic for the parents), to a fox a dead animal is food, regardless of whether it’s a human or a deer.

When prey numbers (especially voles) are high, foxes may gorge and there are reports, mainly from gamekeepers, of foxes stuffed with voles. In 1931, Russian biologist Sergei Ognev, for example, wrote of one fox stomach containing 40-60 voles, while Robin Page -- in his 1986 book, A Fox’s Tale -- told of a gamekeeper at Windsor Great Park in Berkshire who apparently caught a very fat fox; upon dissecting it, 203 young mice and voles were recovered from its stomach. Indeed, throughout much of Britain, voles appear to be the most important small mammal prey species in all seasons. Vole numbers, however, cycle (i.e. boom and crash) in a manner than isn’t reflected in the fox population, because foxes switch to other rodent species and larger mammals during poor vole years.

EarthwormNext, in order of occurrence, tend to be invertebrates, particularly members of the Caribidae (beetles), Lepidoptera (butterflies and moths) and Lumbricina (earthworms), although many other groups, including orthopterids (grasshoppers and crickets), molluscs (slugs and snails) and arachnids (spiders) are also taken. Foxes also seem to have a penchant for rat-tailed maggots, hoverfly larvae (both found in stagnant water) and crane flies (daddy-longlegs). Overall, depending on habitat and season, invertebrate prey can contribute 30% or more of the diet – in desert regions, such as Saudi Arabia, insects may be the primary component of the diet (knocking mammals into second place). Indeed, insects tend to feature highly in the diet during the late summer and autumn months, when insect larvae and earthworms may be eaten en masse; it is not uncommon to find fox scat glistening in the sunshine from all the elytra (beetle wing cases). Insects and worms will often contribute a significant proportion of a growing cub’s diet as summer wears on (particularly during August and September) as the cubs catch them in the vicinity of the earth. In a fascinating 1980 paper to the Symposia of the Zoological Society of London and his equally fascinating book, Running with the Fox, David Macdonald described his observations of fox worming behaviour (i.e. worm hunting). Macdonald found that, during some months, earthworms may account for more than 60% of a fox’s calorific intake (if you consider the average worm yields about 2.5 calories and the average fox requires about 500 per night, this equates to some 120 worms in a night) and, walking at an average speed of a metre (3.5 ft) every 2.5 seconds, the fox can apparently fill this quota in less than an hour in good worming conditions. That said, he did suggest that hunting for earthworms in certain (poorer) parts of the territory is the prerogative of low status or younger foxes – we will come on to this later as we discuss reasons for fox dispersal.

The problem with worms as prey is that their availability is unreliable, varying with the habitat and prevailing weather conditions. In Macdonald’s study area of Boar’s Hill, Oxford, worms were almost twice as abundant in fields with livestock (and thus plenty of dung to fertilise the soil) than in crop-only or fallow fields. More stark comparisons can be made between cereal fields, which contain about one worm per sq-metre (per 11 sq-feet), and permanent pasture, which can house 15-or-more worms per metre. Macdonald points out that the distribution of worms also changes according to the livestock in the field – horses, for example, deposit their scat in one part of the field and do not graze there, so earthworms are clumped in this region (twice as many earthworms here than in the grazed areas), while cattle drop their dung and graze all over a field, causing the worms to be more evenly distributed. In essence, where in a field a fox chooses to hunt depends on what livestock is grazing in it. Finally, the prevailing weather influences worm abundance and distribution, with fewer worms found on windy, dry and/or cold nights. Indeed, warm, still, damp nights are best for worming as eight or more worms per sq-metre may surface in good pasture. Macdonald found that most worms were eaten during February, with the fewest in July, although this varied substantially with the territory (one group were eating some 150 worms each per night, while their neighbours were eating only 25 each per night). Where worms are eaten in large quantities the scat may contain a considerable amount of soil, released from the worms’ stomachs as they are digested.

Birds are next in our list and, as with most other prey species, the frequency with which they are taken varies locally and often seasonally. In fact, birds represent an interesting case because it has been suggested that they (even domestic fowl) are not a preferred prey item of foxes. Birds, it seems, are predominantly taken during the spring and early summer, when foxes have hungry cubs to feed. In a seminal 1969 study of the diet of fox cubs in Sweden, for example, Jan Englund found that mammals (mainly voles and hares) and birds (including gamebirds, poultry and thrushes) were the most important food items in all her study areas. Torbjorn von Schantz, also working in Sweden, found something similar (birds were an important food for the cubs), but also noted that the adults rarely ate birds, although they frequently caught them to feed to their cubs. Of the ‘large birds’ listed in von Schantz’ study, 25% were Common pheasants (Phasianus colchicus) and the vast majority (70%) of these were taken during the cubbing period. Indeed, it appears that adults bring larger items (such as poultry) back to the cubs, while eating smaller species themselves. This implies a shift from a ‘time maximizing’ feeding strategy (i.e. taking whatever’s most abundant or easiest to catch at the time) to an ‘energy maximizing’ one (seeking out prey of higher calorific value, even if it’s more difficult to find or catch) and this could explain the taking of seemingly unwanted prey, such as birds, at certain times of the year. Either way, the suggestion is that the majority of the birds go to the cubs and David Macdonald found that his hand-reared vixen cub was uninterested in eating chickens once she reached three months old.

Fox standing on hind legsDespite the foregoing, in some regions (particularly forested habitats) adult foxes will frequently take birds, and biologists in California found that bird remains (namely duck and small passerines) were found in 70% of fox scats collected from built-up areas (egg shells were found in 5% of scats). They may also cause considerable damage to colonies of nesting birds -- although, again, this is often most pronounced when they’re feeding cubs -- especially if bad weather causes the birds to sit tight on their nests, allowing the foxes to walk right up and grab them. The wild birds most often featuring in fox diets tend to be Passerines (‘song birds’, such as blackbirds, robins, starlings, etc.), Columbiformes (doves and pigeons), Galliformes (chickens and water fowl), Larids (gulls) and Charadriiformes (wading birds), although other species are occasionally taken. In his 1968 book, Wild Fox, Roger Burrows described finding a cache of a Tawny owl (Strix aluco) half-buried in dead leaves; he doesn’t mention whether it was an adult bird but, assuming so, it was presumably scavenged as a mature Tawny owl would seem more than a match for a fox. Alternatively, the fox may have found the bird injured, enabling an easier, less risky capture. Indeed, Burrows twice recovered lead shot from the scat of his local foxes that also contained feathers, suggesting that they had taken birds ‘winged’ (i.e. shot and injured but not killed) by landowners. Foxes will take gamebirds, particularly pheasants and grouse when the opportunity arises and, in one rural area of north-east Dorset, Game Conservancy biologist Jonathan Reynolds found that such fowl accounted for about 16% of the diet. This is discussed further in the Interaction with other Species section.

Foxes will also eat plant material, with fruits (especially berries) being important components of their autumn diet. Blackberries (fruits of plants of the Rubus genus) are apparently much favoured by foxes and, in his 1980 book The Red Fox, Huw Lloyd described how his colleague, Bernard Williams, while studying fox stomachs for the presence of parasites, found one: “stuffed full from end to end with nothing but blackberries”. Indeed, foxes can be very resourceful when it comes to obtaining fruit, including climbing trees and, as the fantastic photo (right) by reader Steve Barker from Middlesex shows, they may even stand on their hind legs to reach blackberries higher up on the bush. It appears that foxes can also be very gentle when removing berries from the bush and, describing his first encounter with a fox, during August 1944, badger biologist George Pearce wrote the following in his book Badger Behaviour Conservation and Rehabilitation:

I was standing by an oak tree when I spotted a fox walking very slowly along a hedgerow, stopping from time to time, reaching into the hedge to bite off a blackberry. Not a single leaf moved, so gentle was it when picking the fruit.”

I have found fox scat that is almost jet black in colour and stuffed full of blackberry seeds, while I have received photos from readers showing scat equally full of other fruit seeds, particularly cherry stones. Foxes will eat both wild and cultivated fruits (in some instances vegetables and crops, such as corn and barley, too) and those most commonly consumed include blueberries, blackberries, raspberries, cherries, persimmons, mulberries, apples, plums, grapes, dates and acorns.  Yew berries (fruits of the Taxus baccata tree) are also eaten by foxes, apparently without ill effects. Yew berries are composed of a tough seed surrounded by a soft fleshy fruit called the aril – the aril is edible (its bright red colouration attracting many frugivorous birds and mammals), but the seeds are widely toxic to animals, owing to the presence of an alkaloid chemical called taxane. In most species, the aril is digested and the seed passed intact (hence the animal doesn’t suffer any toxic impact), but in the case of the fox, it seems that the fruit may not always be digested. In his Wild Fox, Burrows noted how the foxes of Woodchester Park in the Cotswolds ate substantial numbers of yew berries, but the seed always came through the gut whole, along with the red aril. From photos I have seen of scat containing yew seeds, however, it seems that most of the aril is digested, although conspicuous pieces of red fruit are also passed. The photo on the right below was taken by Bill Welch in Kent’s High Elms Country Park during September and illustrates what I’ve seen elsewhere: numerous seeds with some interspersed aril. Bill tells me he’s seen a lot of ‘yew seed scat’ this year and I agree with his analysis that the scats look “distinctly uncomfortable”.

Yew BerriesFox Scat with Yew Seeds
Foxes sometimes eat yew berries, despite the seeds apparently being toxic to most mammals. It seems that the fleashy fruit (aril) is largely digested (although the faeces may still have a red tinge to it) while the toxic seeds are passed intact.

Other plant material includes nuts (especially hazel nuts), grasses, sedges and tubers. Grass is commonly found in the stomachs and scats of foxes, although it is not clear how much is deliberately eaten (some species are known to eat grass to help remove intestinal parasites, such as tapeworms) and how much is ingested incidentally, while catching and consuming other prey. The incidence of fruit in the diet varies locally and seasonally, but generally accounts for 10% to 30% of the diet, with cereal crops representing only about 1% of the diet. One study in County Kildare, Ireland, for example, found that seeds and berries made up about 15% of the foxes’ diets during the summer, increasing to 25% in the winter. Fruits may also be an important food source for cubs and some authors have linked poor cub survival to poor fruit yields.

While the above prey groups constitute the bulk of a fox’s diet, there are other species that occur less commonly and these include amphibians (particularly frogs), reptiles (small snakes and lizards – a study in the North Caucasus steppes of Russia found these animals made up 30% of the local foxes’ diets) and fish; in his 1968 book Town Fox, Country Fox, Brian Vezey-Fitzgerald described watching a fox use its paw (akin to a cat) to scoop a Golden orfe (Leuciscus idus) out of his garden pond. Those living in coastal regions will search the beach and peripheral environs for dead fish, crabs and other shellfish (including cockles and razor-fish) as well as seabirds. Eggs are also highly-prized by foxes, presumably for their protein, fats and cholesterol, and are often carried away and buried (cached) for later use. Indeed, if you wake one morning to find an egg buried in your flower border or bedding pot, it is almost certainly the work of a fox. Foxes generally take (wild and domestic) bird eggs -- on occasion, causing damage to the nests of gamebirds -- but they will also take the eggs of reptiles. During July 1992, for example, David Macdonald and colleagues studied 28 Loggerhead turtle (Caretta caretta) nests on Dalyan Beach in south-west Turkey and found that 25 (89%) were raided by foxes.  Interestingly, nests were invariably raided by a single adult, with most (88%) eggs being cached individually in shallow scrapes further up the beach, but were recovered by an adult and cub, suggesting that the eggs were being cached to feed offspring. More recently, in a paper to the journal Oryx during 2011, David Kurz at Princeton University , USA and colleagues reported on how best to protect Loggerhead nests from mammalian predation. Kurz and his co-workers setup a series of artificial nests along a stretch of beach on North Carolina's Bald Head Island; some nests had chicken eggs, some bacon and chicken scraps and they covered some nests with plastic fencing, some with wire cages and left others (the controls) open. The biologists found that foxes attended all sites equally (based on scat and footprints), but successfully predated only two (25%) of the eight nests covered with plastic screen and couldn't gain access to any with mesh cages, even when they were highly motivated (i.e. going for meat-filled nests smeared in either bacon or chicken grease). In contrast, all control nests were raided. The researchers concluded that plastic screening was effective at protecting turtle nests from foxes (which they found to be by far the most significant mammalian nest predator on the beach) and had the benefit that the plastic composition of the screens wouldn't interfere with the hatchlings' magnetoreception, as galvanized metal cages are thought to. Along similar lines, I have heard stories of foxes eating frogspawn, but have yet to find any empirical evidence for this, although it is quite well known among cats.

Fox scavenging deer carcassFoxes are not oppugnant to taking carrion and, where they share their territory with larger carnivores (lynx and wolves, for example), they may shift their diet more towards scavenging from their kills. They will also make use of any animals killed on roads or by hunters. Indeed, following 641 miles of fox trails on three study areas in Michigan, USA, during two winters, led wildlife biologist Ray Schofield to 61% of the deer carcasses marked (i.e. shot, but not collected) during the hunting season. In their Mammals of the Soviet Union, Vladimir Heptner and Nikolaï Naoumov noted that foxes feed on carrion only in the late hours of the evening and overnight, leaving at sunrise (often to lay up nearby, where it may remain for several days, visiting the carcass periodically) – if the carrion is visited by wolves the fox, according to Heptner and Naoumov, follows after them early in the morning. Indeed, a carcass may occasionally attract several foxes that will feed together; it is unclear whether such aggregations of an ordinarily territorial species consist of related individuals, although some reports suggest not. In his book, British Wild Animals, for example, Mortimer Batten described “a dozen foxes” surrounding a dead stag killed by the harsh conditions in the Highlands during the memorable winter of 1947. Batten wrote:

One or two of them were lying down, tidying themselves or gnawing the ice from between their toes. Others were bickering, and their yaps and yells sounded strange in a silence which seemed veritably to hiss. One was rolling in the snow in the centre of the frozen burn, and others were gnawing lazily at the stag. They had clearly eaten their fill…”

In the Highlands of Scotland, foxes typically live singly or in pairs, so a group of 12 would indicate multiple neighbouring animals making use of this food resource.

A recent study by Rebekah Ruzicka and Michael Conover at the Utah State University in the USA suggests that the weather conditions and the landscape in which a carcass is lying impact how easily a scavenger can track it down. The reason for this is that wind speeds above about three metres per second (6 knots) causes air mixing and turbulence, which dilutes odours, making them more difficult to follow. Indeed, it has been calculated that ideal scavenging conditions occur at wind speeds of between one and four meters per second (2 - 8 knots), with cool, humid conditions to allow the scents to linger in the air and on the ground. In contrast, hot, dry conditions cause scents to be quickly vapourised and dispersed within a few minutes. In a paper to the journal Ethology earlier this year (2012), the biologists present data from their study in which they distributed chicken eggs and dead starlings in various different habitat types around the Willard Bay Reservior between May and August 2009. The researchers found that 66 eggs and 87 starlings were eaten by raccoons, foxes and skunks; the baits hung around for longer as wind speeds increased and they concluded that:

"... red foxes, striped skunks , and raccoons were better able to find bait when it was cool and humid, presumably because such conditions cause scents to linger."

Foxes will occasionally scavenge carcasses of their own species. Some authors have suggested that this happens during particularly harsh winters, although Stephen Harris observed cannibalism in the relatively food-rich habitat of suburban London (fox remains in six stomachs, accounting for 0.6% of the total diet), as did Brian Coman in Victoria, Australia (fox remains in 27 stomachs, accounting for just under 3% of the diet). Roger Burrows described how foxes excavated and removed the bodies of foxes and badgers buried in his garden, in one case removing the head of a dead fox. I have heard similar accounts of foxes digging up the bodies of foxes buried in people’s gardens, which has led to the suggestion that foxes may bury their dead (i.e. remove the bodies from the garden and re-bury them elsewhere) – this seems unlikely and scavenging is a more probable explanation. Infanticide (the killing of young of your own species) is a relatively well-known phenomenon among foxes (see Q/A), but there is no evidence, that I know of, to suggest adult foxes actively hunt and kill each other for food. Similarly, European badger (M. meles) remains sometimes appear in fox scats and stomachs, but do not constitute significant dietary components and are invariably scavenged.

Foxes are well known to scavenge in urban areas, where they will consume human refuse but, even in rural areas, scavenging human waste is well documented. In rural Japan, for example, Paolo Cavallini found that foxes spent between 20% and 50% of their time active around the houses of nearby villages, moving quickly from village to village – some 50% of their diet was of human origin. Indeed, the percentage of human-derived food in the diet varies considerably according to region and season, from nothing (or only a few percent) among foxes in very remote regions, to 80% or more among foxes living in large cities.

A study by Stephen Harris, published in Mammal Review during 1981, looked at scavenged items found in the stomachs of 571 foxes caught in London, finding that meat and bones from joints and carcasses composed 18.4% of the diets. Interestingly, Harris found that 34% of the diet was composed of wild birds and mammals (mainly voles, squirrels and blackbirds), so even in the city foxes were hunting normal wild prey. Bread, dried fruit and potato peelings were also present, representing 3.1%, 2.4% and 1.6% of the diet respectively. A similar study, this time by a team led by Patrick Doncaster and published in the Journal of Mammalogyduring 1990, looked at the feeding ecology of foxes in Oxford (UK) and found a higher percentage (about 60%) of scavenged items in their diets. Interestingly, Doncaster and his co-workers found that, at some sites where food was provided by residents, scavenging foxes were highly selective, discarding some edible items in preference for others. Harris and Doncaster both reported that no single species or category was dominant in the diets of these ‘city slickers’. A study of foxes living in the Swiss city of Zurich was published in Mammalian Biology during 2004 by a team at the University of Zurich, and reported on the contents of 212 fox stomachs, finding similar values to Doncaster and his team, although with some dominance of food types observed. The researchers found that scavenge (primarily scavenged meat) and cultivated crops (especially apples, plums and cherries) were the primary components of the diet, comprising nearly 62% of stomach contents – furthermore, almost 60% of the stomachs examined mainly or exclusively contained one of these items. Rodents and birds were also present, occurring in 26% and 24% of stomachs, respectively. Insects (17.5% of stomachs), pets or domestic stock (10.4%), pet food (6.1%) and bird seed (9.4% - found from January to March only), were also found. Even in the 'urban zone' of the study, "natural food" (namely birds and wild mammals) still contributed 20% of the foxes' diet. Furthermore, the biologists didn't see foxes exploit bin liners regularly or systematically, suggesting that they were opting for less exposed food sources. Some studies of urban fox diet have recorded inedible items, such as food packaging (e.g. aluminum foil, plastic, and paper) in the diet. One study in California's Orange County during the early 1990s found the remains of human food and food packaging in 42% of fox scats recovered during the spring, rising to 86% during the winter; unfortuantely, the authors don't split out the two categories, so we don't know how much of this percentage was the packaging and how much was the food it contained.

In urban areas, foxes are also known to raid dustbins for scraps, although much less frequently than many people realise. Much of their diet, however, is deliberately supplied by householders; many people gain considerable pleasure from feeding their local foxes and a survey in Bristol found that 10% of households were putting out food for foxes every night during the early 1990s. How likely a resident is to put food out, however, depended on how often they saw the foxes – the more often the householders saw foxes, the more often they put (and often the greater the quantity of) food out. It would be interesting to know whether the recent economic recession across much of Europe has impacted the amount of food available to wildlife.

Wheelie BinsFox Feast
Much has been made, in recent years, of how much foxes living in our towns and cities rely on our bins as a source of food and how the introduction of 'animal proof' wheelie bins (left) has removed a major food source for foxes and will result in more attacks on pets. Foxes do raid bins occasionally (although less often than many people realise), but there is no evidence that any of this has happened. Indeed, so many people deliberately feed wildlife, foxes in particular (right), that most foxes would have no need to raid a bin.

So, from the above, we can see that the widely held notion that foxes in our towns and cities survive solely by raiding our bins, or picking up the food dropped by revellers every Friday and Saturday night, is inaccurate. Even in the middle of our large towns and cities, foxes are still hunting birds, mammals, amphibians and insects, despite not apparently having to. Indeed, Harris and his team have demonstrated that, in Bristol, so much food was deliberately supplied (either specifically for them, or in the form of bird food, pet food, or compost heaps in which to search for scraps and insects), that the foxes could survive without hunting or raiding bins at all – one survey found that, in each territory, nearly three-times the amount of food required by a single fox was being put out every week (see below). With that in mind, recently there has been some suggestion that urban foxes are evolving a different jaw structure to rural animals as a result of scavenging more than hunting; I know of no evidence to support this. An increase in skull size in parts of Europe over the last century has been documented, but this is associated with the availability of large prey species (gamebirds, hares, etc.) thanks to human intervention, rather than a result of scavenging. Moreover, as we have just seen, even in urban areas foxes are still actively hunting other animals. The foxes seen in our towns and cities are, however, often in palpably poor condition and I do wonder whether the urban environment allows a fox to eke out an existence that might not be possible in the countryside. It certainly seems to be the case that food availability in urban areas is less seasonal than in more rural locations, making it more reliable and introducing the possibility that urban animals could live longer, grow larger, extend their range further and breed earlier than their rural counterparts.

Ewe with lambsFinally, on the subject of species in the diet, brief mention should be made of their interaction with pets and livestock. Both subjects are covered elsewhere on this site in greater detail (see: Q/A and Interaction with other Species), so I will do no more than summarise here. Foxes have a notorious reputation for taking livestock; most often this involves chickens and lambs, but there is some evidence that they will occasionally take piglets and there have been sporadic reports of foxes taking pony foals, particularly -- according to Brian Vezey-Fitzgerald -- in the New Forest, although I know of nobody else who has ever found evidence for the latter. How many pets, lambs, piglets and foals are killed by the fox and how many are scavenged after death is unknown. Most of the science suggests that livestock and pet losses to foxes are small, but even the loss of a single pet can cause considerable grief and the loss of a single lamb can represent a significant dent in a farmer’s income. One Cornish farmer told me that every time a fox takes a lamb it’s like taking two £50 notes out of his wallet and setting fire to them!  Similarly, telling someone who has just had their rabbit or lamb taken by a fox that studies show how only about 5% of a fox's diet includes livestock is of no comfort. One thing is clear, however: good husbandry practices (lambing inside, for example) along with targeted fox control can significantly reduce the likelihood of any losses occurring.

In both urban and rural environments, foxes will occasionally breach smallholding security to gain access to chickens, ducks, pet rabbits, guinea pigs, etc. How often such events occur is unknown – there are no recent statistics that I am aware of (most that are frequently quoted in the media are based on surveys conducted in the late 1970s and early 1980s) and in many cases people return to find a scene of destruction, but do not see the perpetrator. The problem is accentuated because it is often difficult to be sure of the animal responsible; that it was a fox is often only assumed. I know of instances where cats and dogs have killed other people’s pets and, in some instances the owners have told me that, had they not seen the attack (or in one case, come home to find the dog still in the chicken coop) they would have assumed a fox was to blame. In my experience people often do not consider stray dogs as a possible culprit when they return home to find the remains of a pet, but the 2011 Stray Dog Survey conducted for the Dogs Trust Charity found that just over 121,000 dogs were collected by UK authorities in the 12 months preceding September 2010; an average of 345 per day!  Similarly, badgers, stoats, mink and birds of prey can cause havoc in a chicken run, all leaving similar destruction in their wake, which makes positively identifying the culprit very difficult. This is not a case of special pleading for the fox – foxes do occasionally kill pets, plain and simple. The point is that, when considering the best husbandry practice for the animals in your care, more than just foxes need to be considered. In the end, if you plan to keep pets in your garden, they must be securely housed (see Fox Deterrence) – we should not expect a predator (be it a fox, a cat, a dog or a badger) to turn down an easy meal just because the prey is owned by a human. They have no sense of right or wrong; to them it’s all just food. I, after all, sometimes get in from work too tired to ‘faff’ about making a proper dinner and reach for a frozen pizza or microwave meal because it’s easier; I’m sure I’m not alone, either.

Cat living with foxes in SurreyWhen we think of pets falling foul of foxes, we tend to picture a rabbit or chicken, but there are occasional reports of foxes attacking cats and small dogs (see Q/A). This, even more than foxes taking livestock, is a highly emotive subject, with some people categorically refusing to believe that it happens. Personally, I have no doubt that such instances happen, but I do not believe that they are common, nor do I think foxes pose a significant threat to cats – my own personal experience (and that of many of my researcher and naturalist friends) is that, when cats and foxes meet, the cat either chases the fox off (and I have seen video of a kitten chasing an adult fox away) or the two ignore one another. I have even had e-mails from readers describing what can only be play behaviour between foxes and both cats and dogs, while Bridget MacCaskill -- in her 2001 book, The Blood is Wild -- described how a vixen cub she was rearing struck up a friendship with her black tom cat; the two apparently often slept and hunted together in the enclosure, sometimes the cat would even steal the vixen’s food. Similarly, a friend of mine sent me some photos (left) of a kitten that appeared to be living with a group of foxes in Surrey before, in December 2005, being caught by an animal charity and re-homed. Interestingly, cats and foxes living amicably together is apparently quite well known. Indeed, in a 1935 paper to the Proceedings of the Zoological Society of London, Ian Rowlands and Alan Parkes note that: "... fox cubs are reared quite well by cats ...". Nonetheless, foxes and mature cats are approximately the same size and hunt for the same prey (small rodents and birds), so the potential for competition and hence conflict is always there. Moreover, cats occasionally kill fox cubs, presumably making foxes more wary (possibly hostile?) towards them during the start of the cubbing season. In early June 2012, I had the pleasure of watching a dog fox that frequently visits the garden interact with one of the neighbourhood cats. The following is taken from my notes on the encounter:

"Fox in garden in drizzle sitting half-way along hedge. Cat appeared from carpark and moved quickly around (hugging CVTS office wall) and through flowerbed, past bedroom window and stopped alongside bush outside living room window. Fox watched cat pass and gave chase once cat had gone out of its view (i.e. reached bush). Fox walked up and down along bush outside bedroom window with back arched rubbing flank against bush (very similar to how a cat rubs against a human). Fox approached cat submissively (arched back, ears flat, mouth open and diverted gaze) and cat hissed and swiped at fox with front right paw; fox leapt back and re-scent-marked bedroom bush. Fox and cat looked at each other for a minute-or-so but fox made no further attempt to interact with cat, and didn't approach cat again. Cat followed fox out of garden."

There are also occasional reports of foxes attacking zoo animals and an inspection report of London Zoo published in October 2010 stated that 11 penguins had been killed in fox attacks during March 2009; the zoo also recorded attacks on their South American mara, free-range chickens and flamingoes. Indeed, in their book Urban Foxes, Stephen Harris and Phil Baker refer to one report of a fox walking down a street carrying a flamingo!

So, essentially, if we were to sum up the diet of the Red fox, we can say that they take prey according to species abundance, although they do show preferences for certain species that may be taken preferentially when the opportunity arises. (Back to Menu)

Prey switching
Young Rabbit washingGiven the opportunistic style of their diet, it is not a surprise to find that foxes will adapt their feeding according to changes in the local abundance of prey species. Mammals often increase in the diet at certain times of the year -- voles increase substantially following hay cutting (after which they’re easier to find), for example -- and when mammals are difficult to come by, the proportion of other species taken is increased to compensate. In most parts of Britain, for example, foxes switched to feeding on voles and rats when rabbit numbers ran low because of myxomatosis; elsewhere in Europe, the numbers of hare, mice and pheasants in the diet increased. Another example comes from a study for the Game Conservancy Trust in Inverness (Scotland) conducted between 1992 and 1996, which found that Red foxes from moorland in south-west Scotland fed on rodents, game birds, lagomorphs, carrion and insects. Rodents were the most frequently occurring food type in each habitat, although it seemed that foxes switched to game birds in years where rodents were uncommon. Similar evidence of prey switching has been found elsewhere.

A study in the Snowy Mountains of New South Wales (NSW) found that foxes were dependent upon small mammals during the winter, changing to insects during the snow-free summer months. Similarly, even if small mammals are still about, other prey species may be taken more frequently if they are in particular bounty (fruits during autumn, for example). In a study of 99 fox stomachs from the Kinchega National Park in NSW, G.E. Ryan and J. David Croft found that mammals (mainly rabbits) dominated the diet for most of the year, with a switch to feeding on insects during the autumn. The authors don’t speculate as to the cause of the shift – there is no indication rabbits were less abundant during this season, but insects were probably easier to catch.   In other studies, only parts of the diet were highly seasonal and, in a review of fox diets published in 2003, Stephen Harris and Phil Baker report that small and medium-sized mammals and birds were the most common prey items in all the habitats for which they had data (arable, pasture, marginal upland and upland) during all seasons, while things like invertebrates, eggs and plants were highly seasonal in their occurrence. Where foxes opted for mammalian or avian prey, they tended to take animals up to about 3.5kg (almost 8 lbs.) in weight.

In essence, what these studies show is that foxes distribute their feeding effort in different areas in a manner predicted by the Optimal Foraging Theory (OFT). OFT predicts that an animal has an innate capacity to modify its feeding and hunting behaviour to get the best returns (in terms of energy) for its effort. There are two primary branches of OFT: energy maximization (i.e. animals seek high energy foods) and number maximization (i.e. animals feed on whatever species is most locally abundant). The data available indicate that foxes lean more towards number maximization than energy maximization. (Back to Menu)

Blackthorn SloesThe influence of age and sex on diet
We have seen that fox diet varies according to location, season, habitat and weather/climate, but what about sex and age? Do males eat different foods to females? Do cubs eat different prey to their parents? The succinct answers are: No and Yes, respectively. Most dietetic studies simply look at remains in fox scat, which makes it impossible to assess the effect of sex (generally age, too), but studies based on stomach contents have typically failed to find any differences between dogs and vixens. That said, there are some data (largely cranial and musculature measurements) to suggest that dogs are capable of taking larger prey than vixens, and may do so in some regions. A recent study of foxes in Finland by Suvi Viranta and Kaarina Kauhala has suggested that, since the introduction of the invasive Raccoon dog (Nyctereutes procyonoides), vixens have taken to catching larger prey than before. The authors suggest that increased competition from the Raccoon dog may have driven the foxes to a more ‘hyper-carnivorous’ diet (i.e. taking more large prey, such as hares and deer fawns). Interestingly, no change was observed in the diet of the dog foxes, suggesting that they were already taking larger prey than vixens.

Many fox watchers have observed that the diet of cubs often differs considerably from that of the adults feeding them. Jan Englund was among the first to record this phenomenon during her three year study on the diet of fox cubs (based on stomach contents) in various parts of Sweden. Englund found that mammals (mainly voles and hares) and birds (particularly gamebirds, poultry and thrushes) were important in all areas, with much greater variability found for deer kids, cats, eggs, fish, insects and reptiles. Garbage and scavenge in the diet ranged from less than 1% to about 20% of the cubs’ diets and, in all areas, they increased the fruit eaten as the summer progressed. Most interestingly, Englund observed that, when out hunting, the adults would bring large prey items, such as hares, back to the cubs, while there was a greater tendency to eat small mammals (voles) themselves. Studies of food remains at cubbing earths suggest a similar trend, with plenty of larger prey remains scattered around (although voles are usually eaten whole, leaving little evidence, and so could be underestimated by such studies). Raymond Hewson, during his studies on the foxes of the Scottish highlands, found that while adults in the west and north-west commonly ate field voles, they preferentially brought lamb carcasses back to the earth for the cubs. Erik Lindström, working in Sweden, saw a similar picture, although he found that voles were brought back more often when they were in abundance locally, with larger prey brought in when voles were in short supply. Lindström concluded that foxes were applying what ecologists call the “central foraging theory”. The CFT predicts that a single prey loader (i.e. an animal that hunts for one prey item at a time) should eat smaller prey on the spot and bring larger/bulkier items back to the young in the den.

Finally there is the question of what the cubs start eating when they’re independent. Many of us still enjoy childhood favourite meals -- those foods we were brought up eating -- even though our palates may since have matured or diversified. There are some interesting accounts of young mammals growing up to preferentially take the species fed to them by their parents. In the early 1970s, for example, Raimund Apfelbach found that captive polecats (Mustela putorius) learnt to recognise what to eat based on the smell – familiar smelling food (i.e. that they were fed by their parents) elicited a hunting response, while unfamiliar smelling prey did not. I’m not aware of any similar empirical data for foxes, but there is some intriguing circumstantial evidence. There is an old adage, for example, that gamekeepers will leave a fox family being raised on rodents alone because the young will grow up to eat rodents, while cubs being fed birds would be destroyed. Similarly, observations by Erik Nyholm of foxes on the islands of Kennit and Kuusamo in the Gulf of Bothnia (northern Baltic Sea) found they would seldom touch other prey if fed on fresh Snowshoe hare (Lepus americanus) meat. Huw Gwyn Lloyd had much the same experience and, in his 1980 The Red Fox, he recounted how his captive foxes were raised on quail and would rather go hungry than eat either rabbit or dog food if quail was unavailable. (Back to Menu)

How much food?
Eggs eaten by fox
The body is essentially a combustion engine: it burns fuel (food) in the presence of oxygen and this provides energy that is used to move us around, keep our hearts beating, lungs breathing, brain thinking, etc. There are lots of different ways to measure this energy, but when we’re talking about the metabolism of an animal, we tend to use either calorie or joule. A calorie is essentially a measure of the heat given off by a process, while a joule is a measure of work done (i.e. to move something from A to B). The calories that we’re all used to seeing in the nutritional information tables of food packets are actually different to the scientific units of measurement – one food calorie is actually equal to one thousand ‘heat’ calories and is hence often referred to as a kilocalorie (abbreviated to kcal).  A single food calorie is roughly equivalent to four joules. The day-to-day activities of animals, from replacing dead cells to chasing down a meal, all require energy and each food item provides differing amounts of energy. Scientists can use various factors (such as the size of an animal, the amount of oxygen it’s using and its activity state) to calculate how many food calories it is using up and, therefore, how many it requires in a given day, week, month, etc. (Photo: Foxes relish eggs for their protein and fat content and can carefully break into them to remove the contents without spilling any!)

The amount of food required to sustain a fox’s metabolism varies according to season and sex. A study of Red foxes in New South Wales (Australia) reported that male body fat reserves peaked at 13% of body mass in June (just prior to breeding) and female body fat peaked at 16% in July (during gestation). The biologists, led by Roy Winstanley at Australia’s Vertebrate Pest Research Unit, found that body fat reserves decreased rapidly in both sexes from September through to November, reaching an average of three to four percent by the time the cubs are weaned. The researchers also found low body protein content from August to November (corresponding to a decline in fat reserves), suggesting that the foxes accumulate fat and protein reserves during the non-reproductive seasons and then deplete them during the reproductive period. A subsequent study by the same authors found that, during autumn, dogs required (28%) more energy than vixens, which is presumably a result of the males increasing their activity as the breeding season gets underway.

The influence of season on energy requirements makes it difficult to calculate the precise daily food calories required by a fox, but several studies have provided estimations. Glen Saunders (now at the Vertebrate Pest Research Unit in New South Wales) and his colleagues, for example, calculated that the amount of energy required to support a pair of foxes in Bristol was 28 megajoules (MJ, or millions of joules) -- equivalent to about 6,700 kcal -- per week, or 2 MJ (470 kcal) per fox per day. To give this some context, an adult mouse would provide a fox with about 60 kcal, while a large chicken egg would offer about 84 kcal – thus, a single fox would need about eight mice or six eggs per day. Studies on wild foxes elsewhere have arrived at higher values (30% higher for dog foxes in New South Wales during autumn, for example) and these are probably a result of these animals having larger territories than those in Bristol. In captivity, energy requirement estimates have also been higher:adult foxes have been found to require about 507 kJ (ca. 121 kcal) per day for every kilogram of bodyweight, while cubs (13 to 14 weeks old) require 934 kJ (ca. 223 kcal). Thus, for your 'average' adult fox, this equates to about 3 MJ (716 kcal) per day, or 21 MJ (5,000 kcal) per week. Perhaps the fact that the foxes were captive signifies rehabilitation, which may explain the increased energy requirements. Regardless, these figures give us an insight into how urban environments are generally more able to support larger fox groups than rural areas.  In their 2000 study, Phil Baker and his co-workers found that the food put out by householders in Bristol represented about 40 MJ (9,554 kcal) per week, per territory; enough to support three foxes!

The number of calories or joules needed by a fox is one thing, but how does this translate into the amount of food eaten?  Again, this is a deceptively complicated subject because different foods provide vastly different amounts of energy, but it is generally considered that a fox needs to eat roughly 500 grams (just over one pound) of food per day. Indeed, a report by a team at the Central Science Laboratory in York, published during 2002, estimated the daily food intake of Red foxes to be between 520 and 569 grams per day, for an animal weighing 5.7 kg – equivalent to about 10% of their bodyweight. Similarly, in his book Red Fox: The Catlike Canine, David Henry noted that foxes can survive on only one pound (about 454g) of meat per day, while Torbjorn von Schantz -- working in southern Sweden -- came up with similar values; the average required by adults and subadults (i.e. those between 6 months and a year old) was 520 grams. von Schantz’s study also calculated that, in the week preceding the birth of her cubs, a vixen needed almost 700 grams (1.5 lbs) of food per day, while other researchers have reported that lactating vixens require twice the daily intake of calories of those that are not lactating.  von Schantz also found that cubs required 130 grams (4.5 oz.) of food each day during their first four weeks of life, increasing to about 320 grams (11 oz.) by the time they’re weaned at around six weeks old, and to 440 grams (just under one pound) at three months old. In their 2003 paper, Harris and Baker calculate that a litter of four cubs will consume just over 570 kg (1,257 lbs) of prey between them in their first year. Foxes have proportionally small stomachs compared with other dogs and the maximum Henry ever observed a fox to consume in a single sitting was about a pound-and-a-half. (Back to Menu)

Fox Siezes Cygnet
Eyes bigger than belly? Sometimes foxes try their luck with larger prey, such as this fox trying to take a mature swan cygnet at the Wildfowl and Wetlands Trust at Llanelli, Wales during August 2011. In most cases, the cygnet would have been more than a match and its parents ferociously protective of it. In this case, however, the cygnet made no attempt to fight back and the parents did little to defend it.

Hunting strategies and behaviour
Now we know what foxes eat, and how much food they need, we arrive at the question of how they go about finding and catching their food. Red foxes are predominantly nocturnal and prefer to hunt late in the evening through until the early hours of the morning; consequently, they tend to have more food in their stomachs at night than during the daytime. Most foxes will patrol at least part of their territory each night, becoming acutely aware of where the best feeding sites are and when new food sources appear in the area. They have a keen sense of smell and this can lead them to carrion, even buried under several centimetres of snow or soil.  A fox’s nose, however, is not only good for leading it to decomposing carcasses. Working on the Ravenglass-Drigg Sanctuary in Cumberland during the 1960s and 70s, Niko Tinbergen found that foxes could sniff out eggs he’d buried along one kilometre of ‘fox highway’. Tinbergen observed that foxes could apparently detect an egg buried under three centimetres (about an inch) of sand from 50 cm (almost 2 ft) away. Foxes can no doubt detect many insect larvae and grubs in much the same way. Thus, it is likely that smell, coupled with regular tours of the territory, is sufficient to find much of their food; especially for foxes living on the open hills, where deer and sheep carcasses are important components of their diet, particularly during the winter. Finding food is, however, one thing; catching it, quite another. In most cases, a fox’s food isn’t just lying around waiting to be stumbled upon – it’s very much alive and very keen to remain that way. Consequently, foxes need to be capable of finding, stalking and catching live prey and this they do with impressive effect. Indeed, the literature is replete with examples of how foxes ‘cunningly’ attract, trick and capture their quarry and, while much is myth, some is very much fact.

Red Fox vertical pounceRed fox rodent pounce
Red foxes have evolved as mousers, with a pouncing angle of around 40-degrees (right). Higher angles are needed to land with sufficient force to break a thick crust of snow (right). The down-side to this method of hunting is that the fox doesn't know what it has until it has caught the prey - unpalatable prey (such as shrews and moles) may subsequently be discarded.

One of the most familiar hunting strategies in the fox’s arsenal is the ‘mousing pounce’, which is employed when hunting small mammals (typically rodents). According to Lloyd, in his book The Red Fox, this pounce appears in a cub’s behavioural repertoire at about six weeks of age, when it’s used to catch insects in the vicinity of the earth. The precise angle of pounce depends on what and where the animal is hunting, but typically the sequence begins with the fox walking slowly with its head and tail low, moving its head from side to side. When prey is detected, the head and tail are raised and the ears cocked forward – the fox remains motionless, listening and watching intently. Once the fox has a good idea where its quarry is, it approaches slowly, stopping frequently to listen and, when it gets within striking distance, it rears on to its hind legs, bends its knees and jumps up, landing with its front paws on its quarry, which is quickly snapped up. In some instances the jump is relatively ‘shallow’, with the fox landing with front and back legs almost simultaneously. In most cases, however, the fox comes down with its front paws first (sometimes it reaches near vertical body position – as shown in Richard Peters’ excellent photo), landing with sufficient force to break a thick crust of snow. When rodents are caught they are generally swallowed whole, rather than being chewed. In his book, Wild Guide, Simon King notes that, if birds are caught, the foxes tend to pluck the breast feathers with their incisors before chewing off the wing feathers with their molars; the latter being harder to pluck.

David Henry, in his Red Fox: The Catlike Canine, analysed the pounce of the Red fox using video footage that he had shot of several pounces. Henry was able to calculate that foxes have a 'take off' angle of 40-degrees (give or take about 6-degrees). This is interesting because conventional physics states that the optimal take-off angle for a missile (i.e. the angle at which it has to leave the ground in order to travel the greatest possible distance) is 45-degrees, so the fox is pretty close to optimal. Henry suggested that foxes may take off at a slightly suboptimal angle because, were they to pounce at 45-degrees, they may become too conspicuous to their potential prey. To my mind it seems reasonable that a fox might also adjust its 'take-off' angle in accordance with its distance from its intended meal – optimal distance is no good if you sail straight over the top of your dinner!  Henry also observed that if the fox needed to land with additional force (to break a thick crust of snow, for example), it would aim much higher: about 80-degrees. Recently, researchers in Germany have found evidence that foxes may be able to use the Earth’s magnetic field to accurately judge the distance to their prey (see: Senses). Once the prey has been caught, the fox will sometimes ‘play’ with the animal before either eating it or letting it go. Henry recounts a fascinating incident from the autumn of 1971, during which the fox he was following pounced and caught a shrew, before carrying it up the hillside and playing with it at a roadway. Henry wrote:

“… the fox is leaping around, dancing about the shrew who runs over to one side of the road before the fox herds it back to the center. After 45 seconds of playing with this animal, the fox then does an extraordinary thing. He picks the shrew up in his mouth, walks back down the slope to where he captured the prey, and then with a toss of the head spits the shrew out directly at a small burrow. In less than a second, the shrew disappears into the hole and out of view.

After this remarkable event, the fox apparently turned casually away and trotted back up to the road where it continued to look for more prey. This encounter left Henry in no doubt that the fox had no intention of eating the prey. Moreover, it raises some interesting questions about the fox’s understanding of the prey animal – it took the shrew back to the burrow from which it was caught, rather than just letting it run off into the vegetation on the roadside and find its own way home. Does this suggest that the fox had some inkling that the burrow was in some way important to the survival of the shrew? We cannot say for sure, and a single encounter is not much from which to draw conclusions, but reading it certainly made me think about foxes in a new light!

A very similar example of a fox playing with a prey item was recounted to me by Tina Rae. The following is Tina's description of the behaviour she witnessed near Glasgow on the evening of 19th July 2012:

"Last night it was funny..well maybe not for the big mouse or small rat; we couldn’t decide what it was.  My one eyed fox had found a rodent and we were watching it poking it to make it run down a hill…when it got to the leafy bit to safety the fox picked it up and took it to the top of the hill again and poked it to make it run again…he reminded me of a cat playing with a mouse.  When he carried it to the top of the hill again he was really gentle picking it up by its tail.  This happened at least 20 times ‘till Velma (his daughter) appeared from nowhere and grabbed the rodent and ran like hell and jumped over a hedge and her dad chased her."

Foxes Play Pouncing (Eric Ashby)As mentioned, pounces are adapted as necessary to catch insects and also birds, but are of little use against larger mammals and soil-dwelling invertebrates and mammals (e.g. moles). Indeed, moles are located, presumably by sound, and dug out, while earthworms are hunted from the surface as they emerge from their burrows. In his 1980 paper, David Macdonald described how the foxes hunted worms by sound, stopping and listening intently before snapping and seizing a worm – once the worm was held firmly between the incisors, the fox paused momentarily before slowly raising its head to pull the worm from its burrow and consume it whole. Macdonald also suggested that vixens may teach their cubs how to hunt worms, and how to tease them from the soil (sometimes rubbing them gently with a forepaw) so as not to snap them in half. Bridget MacCaskill, in her book The Blood is Wild, was also under the impression that parents teach their cubs how or where to hunt, although this may not be entirely necessary – when she placed the cubs she was fostering into an outside enclosure they immediately started catching voles, without having the experience of an adult to show them what to do. In the 2007 Fox UK booklet, published as a supplement to the month’s BBC Wildlife Magazine, reader Elaine Howard from Cheshire described a dog fox teaching one of his cubs how to pick up an egg, while Channel 4's Foxes Live series (broadcast in May 2012) filmed a vixen bringing a live bird back to the earth for the cubs, possibly to provide the opportunity for them to practice their hunting skills. In addition, several naturalists have noted how foxes appear to watch and learn from each other, so a degree of cultural transmission is not unexpected.

Overall, it seems probable that the ability to pounce on prey is innate behaviour -- as is chasing or jumping on moving objects or those rustling in the undergrowth -- that may subsequently be improved through practice and, possibly, guidance from their parents. Indeed, we know that hunting takes time and practice to perfect and as the cubs grow, and the food supply from their parents dries up, they’re reliant on more easily caught prey until they have developed the motor skills and technique required to catch preferred prey. Recent work by the mammalogists at Bristol University has found that earthworms and insects are crucially important prey for newly weaned cubs. Invertebrates provide nutrition in the first month after the parents stop feeding them, as they hone their hunting skills; their availability also influences their cubs’ adult size.

Larger prey, such as rabbits, hares, gamebirds and deer kids tend to be stalked and ‘rushed at’. Watching a fox hunt rabbits is an enthralling experience. The fox crouches low, belly to the ground, and staying low it runs quickly from one area of cover to another, where it stops and resumes the crouch. If no cover is available, the fox stalks across in the open, freezing periodically as the prey looks in its direction. When the fox judges it is within striking distance it ‘explodes’ from its spot and a remarkable race ensues. As the fox runs it employs its tail as a counterbalance, as it twists and turns in pursuit of its prey. Foxes may also lie in wait for their rabbit quarry and the BBC’s Tale of the Big Bad Fox documentary, aired in 1995, showed a fox unsuccessfully hunting rabbits – many rabbits retreated underground while a few look outs above kept a wary eye on the fox and thumped an alarm call. In the gloom of the hedge, the fox lay down and simply waited; after a while the sentinel rabbits went back to grazing and, with no thumping from above, the other rabbits emerged from the warren, allowing the waiting fox to snatch himself a meal. Unfortunately, I have no statistics as to how successful foxes are when hunting rabbits, but I would be interested to hear from readers who have.

Foxes will also take rabbit kittens and, in most cases, these appear to be dug out of the stop (underground nesting chamber) by the fox. In their study of fox predation on young rabbits in northern Holland during the late 1970s, Jaap Mulder and Marijke Wallage-Drees, found that foxes tended to dig directly down into, or slightly to one side of, the nesting chamber, creating a distinctive oval or rectangular hole measuring an average of about 20cm (8 in.) in diameter. Foxes obviously have a remarkable ability to detect the kittens underground and, given that they nearly always dig straight into the burrow, they can pinpoint them accurately under some 40 cm (1.5 ft) of soil; they presumably do this by sound. Perhaps more interestingly, was the finding by Mulder and Wallage-Drees that stop predation was very localised, offering support for the theories of earlier authors that predation of rabbit kittens in stops is not a general habit of all foxes, but a speciality of some individuals.

Foxes hunting hares are less frequently observed, but an account in Robin Page’s 1986 book, A Fox’s Tale, suggests they’re approached more directly than rabbits. Page recounts the experience of a farmworker, who believed that foxes caught hares while they were sitting in their forms by approaching from the front. Page explained:

According to him there were two reasons for this: firstly hares spend much of their time in their forms looking behind them, so they can often be approached directly. And secondly a hare always runs forwards from its form; consequently if the fox gets close enough, the hare runs towards it initially and its chances of escape are reduced as a result.

Sunbathing foxIn folklore, foxes are renowned for letting their food come to them – that is to say, playing dead to attract curious and scavenging animals. In his story of the Springfield Fox, Ernest Thompson Seton described how a vixen demonstrated to her cubs how to catch squirrels; she’d lie “flat and lifeless” on the grass near the base of the tree and wait for the curious rodent to approach within striking distance. Despite an opening note to the reader saying that the stories in his compendium were true, many of Seton’s tales are of dubious authenticity. There are, nonetheless, many similar stories of foxes apparently playing dead to attract prey to within striking distance. A frequently featured victim is a corvid, typically a crow, although the source of such stories is unknown. In their book Urban Foxes, Stephen Harris and Phil Baker mention watching a pet crow belonging to a friend; said crow would sidle up and peck at the pet dog who was trying to sleep. Harris and Baker considered something similar might explain the source of such ‘death feigning’ stories in foxes. That said, there is apparently some footage, captured by a Russian film maker in 1961, showing a fox lying motionless in the grass with its eyes closed; a crow slowly approaches and, very suddenly, the fox springs round, catches and kills the crow. I have only seen stills taken from this film, but the description Rebecca Gambo gives in her 1995 book, The Nature of Foxes, suggests that the crow was targeted by the fox.

Gambo also recounts a similar story by naturalist and photographer Leonard Lee Rue III, who described how a fox will pick up a stick and play with it on the shore in full view of a flock of ducks, seemingly ignoring the waterfowl. After a short while the fox, appearing to tire of his game, drops the stick and wanders off into some nearby reeds; the ducks then come onshore to investigate the stick and are pounced on by the waiting fox. Again, I know of no empirical evidence of this, but apparently this behaviour was so successful and common that hunters on the New England coast of North America bred special fox-like dogs and trained them to ‘toll’ for ducks in the same manner as the foxes – this brought the ducks closer to shore, making them easier to shoot.

Foxes are very intelligent mammals and appear not only to be able to learn from other foxes, but also to learn from their prey. Under such circumstances it seems possible that a fox may ‘catch on’ to the idea of tricking potential prey into striking distance and, with the aid of this ‘cultural transmission’, there is the potential for such behaviours to propagate within a population. This is conjecture on my part, of course, and remains to be demonstrated experimentally, but there are several tantalising examples of foxes learning the behaviours of their prey and applying them during a hunt – problem-solving, if you like. One particular incident was observed during June 1973 in Alaska’s Denali National Park by Selkirk College biologist Peter Ommundsen, who described the event in a paper to the Canadian Field-Naturalist in 1994. Ommundsen watched an Arctic Ground squirrel (Spermophilus parryii) feeding on vegetation when it was approached by a Red fox; the fox charged and the squirrel ducked into a tunnel (the ‘entrance’), evading the predator. Within a minute, the squirrel reappeared at another hole (the ‘exit’), but within view of the fox, and returned to its feeding site. Again the fox charged and the squirrel escaped back into the entrance and shortly emerged from the same exit to resume feeding. The fox was seen to ‘rush’ the squirrel a third time, causing it once again to duck into the entrance, avoiding its pursuer, but this time the fox:

“… ran directly to the exit, where it waited with mouth open. The squirrel promptly appeared at the exit, as it had on the two previous occasions, and was immediately captured by the fox.

This example is quite remarkable because it demonstrates problem-solving behaviour by the fox, and such encounters are rarely observed in the wild. Another example, this time of cooperative hunting, is given by Chris Ferris in her 1988 book, The Darkness is Light Enough. Ferris described how the dog fox would position himself on one side of a favourite rabbiting field and the vixen would launch an attack from the other, catching a rabbit in the process. The appearance of the vixen sent the rabbits bolting for cover, towards the dog fox, who would dart out and catch a couple of the panicked rabbits. This goes above and beyond Ommundsen's account in that there must have been some previous 'planning' and communication of the plan in order for it to function properly. In the late 1970s, Russian researchers demonstrated that foxes were capable of novel extrapolative behaviour in locating food (i.e. when someone moved the food out of view, the foxes started looking for it). This may sound pretty basic, but understanding object permanence (i.e. the ability to realise that something has been hidden and can thus be found, rather than having disappeared) is quite a big deal in behavioural circles and such systematic searches for hidden objects (such as where the heck did I leave my car keys?!) is not something human babies do until they’re about a year old. The researchers found that some foxes were better than others at such object permanence tests. At this point, it's worth remembering that none of this should really surprise us: foxes get hungry and go out hunting for food that's essentially hidden every day. I think there is a tendency for us to view animal behaviour in an overly clinical manner, considering that humans are in some way superior to other animals because we have such domination of our environment. Ultimately, humans are animals too and far from being disassociated with Nature, we are intricately connected to it.  Invariably there is a need to a level of clinical analysis of behaviour, but referring to a behaviour as 'instinct' should not devalue it.

Another aspect of fox hunting behaviour that is oft-cited but often regarded as folklore is that a fox always hunts away from home.  In other words, a fox will never take chickens from a coop in its territory so as not to draw attention to itself. Indeed, in his 1975 book, Thorburn’s Mammals, Scottish naturalist and painter Archibald Thorburn wrote:

I was told that the vixen never interfered with some fowls living close at hand, but would always forage for food at a distance. She was no doubt wise enough to know that her young might be endangered if depredations occurred near home.

This would certainly seem like a ‘cunning’ plan, but I am not aware of any evidence to support it.

There aren’t many statistics on the hunting success of foxes; my own experience suggests this may be at least partly because, even when hunting is observed, prey is consumed so quickly it’s difficult to be sure if the fox was successful or not (particularly when the animal is hunting voles in long grass, giving only occasional views). We do know, however, that hunting success varies with the type of prey being targeted.

Fox drinking from birdbathDuring his numerous walks around the boreal forests of Canada observing Red foxes, the eminent ecologist J David Henry observed 434 completed hunts (i.e. where some attempt was made by the fox to pin and bite the prey) by 22 foxes. Henry noted that 139 (32%) of these hunts were successful and that there was an interesting variability between the success of the fox and the type of prey. Foxes successfully caught insects 82% of the time, mammals 23% of the time, and birds only 2% of the time. It is tempting to suggest that this success rate is probably related to maturity and, hence, experience, as is known in many animals.  A similar picture was revealed by Mark Bekoff and Mike Wells during their studies on coyotes (Canis latrans), which, like foxes, frequently hunt small mammals; they found that, on average, adults were successful at catching rodents about 25% of the time, with considerable variation according to the species they were hunting. When targeting voles, for example, coyotes succeeded in only 18% of hunts, while they caught gophers 83% of the time. Bekoff and Wells also found that hunting success varied with habitat, with coyotes being three-times more successful hunting in short than long grass. An overall success rate of just about 30% is in line with many other predators: compare Golden eagles (Aquila chrysaetos) and Peregrine falcons (Falco peregrinus), which are successful about 20% of the time; Nile crocodiles (Crocodylus niloticus) that successfully ambush Black wildebeest (Connochaetes gnou) about 30% of the time; and Grey wolf (Canis lupus) packs that successfully bring down elk (Cervus canadensis) in 45% or more cases.

Foxes do not have a particularly powerful bite when compared to other carnivorans and prey is typically killed by a bite to the back of the neck, severing the cervical vertebrae. The head may be removed and either eaten separately to the body, or cached for subsequent retrieval. In some cases the head and body may be cached in separate places. Foxes also tend to consume their kills in a fairly predictable manner. Ecological consultant, and experienced naturalist, Dan Lombard described to me his experience of fox kills. The following is slightly modified from his original discussion and reproduced here with his permission:

I find foxes and badgers will break in through the naval, vent, and ventral area -- as opposes to the neck -- and feed around the back of the rib cage. I found quite a good example of this the other day. Foxes tend to eat most of the organs; badgers are pickier and always leave the caecum. This is presumably due to foxes being more able to digest grass, compared with badgers. The head is removed and the organs eaten; I then find the back legs are stripped to the bone, with the foot from the ankle down, left untouched. A lot of the time the fore quarters are left, although again the body may be slit in two and cached apart or together.

Foxes may cache a carcass immediately after obtaining it, or consume part of it before burying the leftovers for subsequent retrieval. (Back to Menu)

Killing to ‘excess’ and the storage of left-overs
Foxes are extremely possessive of their food and, even at an early age, will defend their catches from other (even more dominant) animals. Food may not, however, be eaten all at once and some may be buried for later retrieval – this process, practiced by many animals, is called caching (pronounced “kash-ing”). When an animal chooses to store surplus food there are two main choices it has: it can either store everything together in one place (Larder cache), or it can bury everything individually or in small clusters (Scatter cache). The pros and cons of these are discussed in an associated Q/A, but essentially if you larder cache it makes it easier to recover everything at a later date, but at the same time if someone discovers your hoard, you’re likely to lose everything; if you scatter cache you minimize losses in the event someone else finds it, but you have to remember the location of each cache. Foxes, it seems, show a tendency towards scatter caching, although there are exceptions. The question, though, is why should a fox want to cache anything?  Well, the answer is that foxes aren’t fortune-tellers; they cannot see into the future and know whether they’ll be successful hunting tomorrow. Consequently, foxes hedge their bets – when a fox comes across a bountiful food source, such as a coop full of poultry, rather than thinking “I’ll take one of those and come back tomorrow for another” (by which time the defences could’ve been fortified or the birds moved), it often sets about killing all the birds. Once dead, the fox will move the birds out of the coop to store for subsequent retrieval, when pickings are slim. In fairness, this is not far removed from us going to the supermarket once a week to stock up with food.

Now, while reading this, some of you will no doubt be thinking along the lines of: “I’ve had a fox raid my chicken coop and it left some/all of the birds where they fell.” Unfortunately, this happens from time-to-time and, while also being very distressing for the owners of the birds, it has earned the fox a bad reputation as an animal that kills for fun or sport. Could this be true?  Well, at the risk of appearing pedantically controversial, I would say no. Ultimately, the reason for the initial kill is simple: to get food. The subtle, but crucially important, point is that just because a fox’s motivation for the kill isn’t fun or sport, it doesn’t preclude enjoyment on the part of the fox. Indeed, in his A Fox’s Tale, Robin Page was convinced that in some instances foxes do enjoy such surplus killing and, after watching a fox in his chicken shed, he wrote:

“… the fox I had seen was clearly enjoying itself – it was playing.”

Upon reading the above quote, some of my ‘pro-fox’ friends will be horrified, while some of those ‘anti-fox’ ones will feel vindicated. The point I’m getting at, however, is that I do not believe that a fox kills for fun (it kills for food), but that doesn’t mean that it cannot enjoy the kill itself. It may help to think of this a little differently. Most people go to work each day for a simple reason: they need money. The fact that your reason for going to work isn’t to have fun (it’s to secure enough money to provide for yourself and your family) doesn’t mean that you can’t enjoy your work. This is a pretty basic example, and I know there are various exceptions, but I hope it helps clarify my point that a predator can enjoy a hunt, without the purpose of the hunt being enjoyment. Certainly, it would be foolish to assume that foxes hated killing other animals – they’re predators after all, and a predator that stops to consider the ‘feelings’ of its prey is rapidly evicted from the evolutionary ‘arms race’. Likewise, an animal that risks injury and wastes energy frivolously killing something it has no intention of eating or feeding to its young is almost certainly playing a losing hand. Whether foxes actually enjoy killing I do not know, but I suspect their genes have equipped them with a chemical reward (dopamine release in the brain, perhaps) for securing the food that keeps the body alive, as our genes have us. So, if we assume that a fox enjoys dispatching an entire coop of chickens, does that make it evil or malicious? No, of course it doesn’t. Foxes aren’t human – they have no moral or ethical code and, as such, no sense of right or wrong. They are predators, pure and simple, and they thus survive by killing and eating other living organisms. Judging their actions by our own standards is, quite frankly, destined to achieve nothing but bad feeling.

Rabbit in fox cache
A rabbit leg protruding from a shallow fox cache. The integrity of fox caches varies considerably from fox-to-fox and even those made by the same animal at different times. In some cases great pains are made to conceil the cache (even going so far as to remove traces of footprints), while at other times (particularly, although not exclusively, in urban areas) caches are remarkably haphazard.

Now, getting back on track after that brief, but important, detour, we arrive back at the question of why the bodies of the poultry are sometimes left in situ? The answer, I think, is that the act of caching the bodies is a slow one, as a fox will generally be able to remove only a single bird at a time – worse, for the fox, the gap that it managed to squeeze through may be too small to pull a chicken through, forcing the fox to leave empty handed. Assuming the fox can get the birds out, much can happen in the time it takes to bury a chicken: the owner may have been woken and come to investigate or remove the bodies; the fox may have run into trouble (another fox, or dog, for example); or it may be unfortunate enough to end up being killed or injured trying to find somewhere to bury its prize. Whatever the reason, sometimes the fox won’t return but in most cases I suspect they try. Martin Hughes-Games, on the BBC’s AutumnWatch series of 2010 mentioned that after a fox got at his poultry he left the chickens where they fell and the fox came back and collected them all. I have heard similar accounts from WLOL readers and in March 2010, for example, Sue Stephenson e-mailed me with her experience. Part of Sue’s e-mail is reproduced below with her permission:

With regards to the mass slaughter and leaving of carcasses - I've always thought, in fairness to the fox, that they probably did intend to come back for all the dead chickens. A couple of years ago a fox got into the run and killed 6 point-of-lay hens. It was in July 2007 when we had the floods and with the water pouring into our kitchen I couldn't spare time or the heart to deal with the dead birds but the following day when I returned - all the bodies had gone.

The subject of surplus killing and the various explanations for the behaviour are covered in an associated Q/A, so I won’t delve any further into the topic here. The caching behaviour of foxes has been widely studied and we now know a great deal about what foxes cache, when they retrieve the caches and how they remember the locations of all their caches. These questions are also dealt with in a Q/A, so I will only summarise the details here.

Fox cub caching foodCaching tends to involve a fox digging a hole with its front paws, placing the object into it and then pushing the soil and vegetation on top with the snout. Observations of wild and captive foxes have shown that the desire to cache food appears at about six weeks old and that the appearance of the cache varies with age (adults being more proficient at concealing a cache than cubs) and how hungry the fox is – satiated foxes tend to make rather haphazard caches.  An item may be cached even when the fox is still hungry and it seems that preferred foods are more likely to be eaten on the spot, while less palatable morsels are cached. Broadly-speaking, foxes recover their caches within a day-or-so, although Tinbergen found that some of the gull eggs cached on his dune study site were recovered up to two months later. In Bristol, Stephen Harris found that most caches were excavated on the following night, with studies elsewhere showing that almost all are recovered within a week of burial. One fox’s cache may occasionally be raided by another fox, although the ‘cacher’ is often very careful at concealing the cache site -- even to the extent of walking backwards brushing paw prints away as they go! -- and David Macdonald found that other foxes were generally unsuccessful at finding caches that weren’t their own. Macdonald also observed that foxes may dig up and relocate a cache if they think someone’s wise to its location. When it comes to relocating a cache, it seems that foxes rely heavily on their memory, rather than just remembering the rough area (based on landmarks) and then letting their nose lead them to the exact spot. Macdonald found that when he cached another mouse within three metres (10 ft) of his vixen’s cache she found only about 20% of them (but recovered 90% of her own caches), and when he dug up her cache and moved it one metre (3 ft) away she only found one-quarter of them. If she was relying on her nose for the last stages of the recovery she should surely have found both the additional and transplanted caches.

Several authors have noted how foxes not only seem to remember what is in a particular cache, but seldom return to an empty cache. It is possible that foxes remember which caches they have excavated and which they haven’t, but during his studies on the boreal forest foxes of Canada, Henry proposed an alternative explanation. Henry suggested that foxes urinate on caches once they’ve excavated the contents and know that the smell of urine means there’s no food left and it’s not worth wasting time digging – in other words, the foxes use this scent-marking as a kind of cache book-keeping system. Henry noted that, for the most part the system seemed to work, but in some cases the smell of food must have been so strong that the fox dug anyway.

So, in summary: foxes are opportunistic predators, with a strong tendency to feed on small and medium-sized mammals. They will scavenge if the opportunity arises but, even in heavily urbanised areas, they actively predate mammals, birds and insects – contributing about 20% of their diet. Pets and livestock are occasionally attacked and foxes may engage in surplus killing when conditions permit, but the desire to cache surplus food probably evolved in response to this ‘surplus killing’ behaviour. (Back to Menu)

Rural Red fox

Breeding Biology: In the Northern Hemisphere the breeding season for Red foxes typically runs from November until early February, although there are exceptions, with some vixens reported in season as early as mid-October. Indeed, both early and late breeding have been recorded in foxes and this is a topic researched by former MAFF biologist Huw Gwyn Lloyd. Lloyd calculated that vixens come into season from about 94 days after the summer solstice, which means they can come into season any time from late September. In a study of 610 vixens from Wales, Lloyd found two had conceived during early November, while a vixen shot on Boxing Day 1962 at Llandudno was near full term, suggesting she’d mated during mid-October. A few Welsh vixens were found to be pregnant during mid-April (suggesting conception during late February) and there are unconfirmed reports of pregnant vixens in July, August and September. In a 1989 paper to the Journal of Reproduction and Fertility, Mats Forsberg and his colleagues report that long summer days followed by short winter ones are required to ‘reset’ the foxes’ breeding season and that artificially manipulating the photoperiod (i.e. the length of the days) or manipulating melatonin levels by injection can prevent testicular regression and extend the breeding season. Thus, it seems that it is an increased sensitivity to shortening day length, possibly coupled with a drop in average temperature, which triggers breeding in the Red fox.

The precise timing of breeding is, as we shall see later, closely tied to the condition of the vixen, and so the breeding season may be delayed where food supply is intermittent. Working in Scotland during the 1970s, for example, Hugh Kolb and Ray Hewson found that foxes bred later in the west of the country than in the north-west; they considered this was an adaptation to a more intermittent/unpredictable food supply (voles, in the west). Generally speaking, foxes in the north of the species’ range breed progressively later than those farther south – in the UK, Scottish foxes may breed up to one month later than those in the far south. Thus, at high latitudes, the breeding season may run into late March, although most of the mating activity occurs during December and January; in the UK, dogs are at the peak of their reproductive potential during January. (Back to Menu)

Reproductive development
Dog foxes begin the entry to breeding condition in August, as the production of sperm resumes following a hiatus during the late spring and summer months – accordingly, the testes have increased in size by around six-fold come December (from 1-2 grams to 7-8 grams). The greatest quantities of mature sperm are produced during December and January, after which sperm production reduces; sperm may be present in the epididymis until April (some studies have found sperm in every month) but will have deteriorated to such an extent as to be largely useless. It seems that foxes undergo significant increases in testes size, and invest relatively more energy resources into producing sperm-making tissues, because there’s a high demand for sperm given the brief period during which this species can breed.

Red fox baculumLike most mammals (including dogs, cats, hedgehogs, bats, rodents and non-human primates), dog foxes have a bony structure in the penis called a baculum (or ‘os penis’ - left). The baculum is a heterotrophic skeletal element -- in other words, it’s not attached to the skeleton -- that has a rough base and a deep groove giving it a V-shape in cross-section; it serves to maintain an erection during intercourse. The baculum bends down towards the tip by an angle of 10 to 30-degrees and grows as the fox matures, reaching its full length (4 or 5 cm / 2 in.) at just over a year old. During mating, a bulb-like mass of tissue surrounding the baculum tip (called the bulbus glandis) swells as it engorges with blood and the pair may become locked (or tied) together – this is known as a copulatory tie and is present in most canids. While copulatory ties do not always occur, when they do they can last anywhere from a couple of minutes to more than an hour (90 minutes is the longest I have come across in the literature).

Studies on the sperm of the captive foxes by Russian researcher I.D. Starkov during the 1930s found that the average dog fox ejaculated 6 millilitres (mL) of semen each time and that this contained in excess of 300 million sperm (usually 200 to 500 million). There was some variation in volume, with immature males producing less semen (2.5 mL) than mature animals; the largest volume Starkov recorded was 22 mL. Subsequent studies by Finnish biologist Liisa Jalkanen showed that ejaculated semen is composed of three fractions, with sperm making up only one or two mL. To give this some context, a teaspoon is 5 mL and an adult human will ejaculate up to about 10 mL. In a 1993 paper, Jalkanen presented data on her analysis of 161 ejaculates from 36 adult silver foxes – she found that, on average, 88% of the sperm in an ejaculate were normal and, of the 12% that were in some way abnormal, more than half had a defective flagellum (tail). Jalkanen also found that dogs in their first breeding season had fewer sperm (more of which were defective) than mature males. In another study, also on captive foxes but this time on a Polish farm during the late 1940s, Zbigniew Wolinski found that males were usually capable of inseminating vixens for between seven and 18 days (although some up to 48 days) per breeding season, with most matings occurring during mid-February. It seems that mating in the 24 hours after ova are shed by the female offers the highest chance of conception in the fox so peak sperm production must be closely tied with ovulation of the vixen.

Red fox vixens are monoestrous spontaneous ovulators; in other words, they come into season once a year and ovulation is triggered by changing season (short-day breeders), rather than by the presence of a male or the act of mating. In a minority of cases (about 1%) on fur farms, vixens have become sexually receptive twice in a single year, but there is no evidence of this from the wild. The ovaries of vixens increase in weight from the end of June until the end of November, although they can start coming into oestrous (or “season”) during October. The oestrous lasts for around three weeks and during this time there is a critically important phase, lasting for about three days (ranging from one to six days), during which the vixen is receptive to fertilization: this period is called estrus (or “heat”), and is one of four phases that make up the oestrous cycle. Vladimir Heptner and Nikolai Naoumov, in their 1988 Mammals of the Soviet Union, note that strong frosts and snowstorms delay estrus and that there is a significant change in intensiveness of the ‘rut’ in the forest zone of the former USSR. In favourable years, according to Heptner and Naoumov, concerted estrus took place in the course of one month while, during unfavourable years, it expanded to two-and-a-half months.

According to Lloyd, in the absence of a successful mating, the vixen will revert to anoestrus (i.e. will no longer be receptive to breeding) after a period of ‘pseudo-pregnancy’ of up to 40 days, during which she may even lactate. Studies on captive vixens have demonstrated that older females come into estrus earlier (by around a week) than younger ones and Wolinski found that there was no decline in fertility until a vixen reached eight years old (an achievement few wild animals will see). Working in suburban London, however, Stephen Harris observed a decline in breeding performance in vixens by their fifth or six year. (Back to Menu)

The number of breeding vixens
Mating Red foxesThe question of how many vixens in a population will come into oestrous and what controls this at the population level is an interesting one. Conventionally it has been considered that, where several vixens coexist, only one (dominant) female will breed and that she suppresses the reproduction of any others. Quite how the vixen does this was a matter of some debate, but one suggestion was that she restrictes subordinate access to food. Indeed, there is a well-known connection between food availability and breeding condition in foxes. In the early 1940s, for example, Russian biologist A.F. Chirkova recognised that food availability played an important part in reproductive success in foxes; she noted that, in poor food years, females would not come on heat, that ova (eggs) wouldn’t be fertilised, and that sporadic losses of embryos would occur. Subsequent work by Erik Lindström in Sweden during the 1980s revealed a similar picture; he demonstrated how productivity was related to food availability such that vixens in good condition were more fecund and lost fewer foetuses than those in poorer condition. Furthermore, Lindström found that the yearly ovulation rate in his study population was closely correlated with the vole supply at the time of cub birth (in spring), suggesting foxes could “anticipate future food supply”. Lindström suggested that the foxes may be able to react to the presence of reproducing voles during the winter, which signifies a subsequent ‘peak’ in the cycle. In a 1988 paper to the journal Oikos, he even goes so far as to propose a mechanism, suggesting that small quantities of vole reproductive hormones ingested by the fox could be the trigger for the 30-40% increase he observed in fox fecundity.

It would seem, however, that the availability of food and condition of the vixen is not the whole story and, in his paper in the 1980 Biogeographica on fox ecology, A.V. Braunschweig noted that, in agricultural areas of central Sweden, nearly all vixens ovulated each year, but a high proportion (40% to 64%) were barren, even when rodents were abundant. Similarly, a 1996 study in the Pisa province of central Italy by Paolo Cavallini and Simona Santini found that, although larger vixens generally produced larger litters than smaller ones (a commonly observed trait), body mass (i.e. subcutaneous fat levels) wasn’t correlated with ovulation rate or the number of ova or foetuses lost. In other words, breeding performance was not affected by how well-fed these vixens were – something else was at play.

Seven years before Cavallini and Santini’s investigation, Erik Lindström had formulated a theory that, while the breeding of vixens at high latitudes was limited by food, those further south were being limited by social stresses – i.e. the dominant vixen was harassing any subordinate vixens to such an extent that they either didn’t conceive, or lost their embryos. In 1994, a team of biologists -- fronted by Bristol University’s Gill Hartley -- published their observations on the endocrinology (the production and action of hormones within the body) of captive foxes in the Journal of Reproduction and Fertility. Hartley and her co-workers kept 11 orphaned vixens and seven males in family groups (i.e. one sexually mature dog, with mature vixens where mother-daughter relationships were maintained) and found that only one vixen in each group successfully produced cubs. All the vixens came into oestrous and were mated, but those that failed to breed (i.e. didn’t implant their fertilised ova) showed changes in the levels of two important hormones: a reduction in progesterone and high cortisol levels. Progesterone prepares the uterine lining to receive the ova and without it pregnancy cannot be maintained, while cortisol is an adrenal hormone that is produced in response to stress. Essentially, Hartley found evidence suggesting that the non-breeding vixens were ‘stressed out’ by the dominant ones and this caused a change in their hormones that caused them to abort their fertilized ova around the time of implantation. Observations on fox populations from across their range have shown that within-group aggression increases towards the breeding season and it is possible that this increased hostility of the mother towards her daughters causes the rise in cortisol and associated drop in progesterone that drives this social stress mechanism.

The data collected by Hartley and her colleagues may be only part of the answer to the question of why some foxes fail to breed even when food is abundant. We know from the studies on Bristol’s foxes that, in some urban populations at least, subordinates do mate and many conceive. Interestingly, unless there is a super-abundance of food or the dominant vixen is killed, about 20% of these subordinates abort their litters very late term (rather than at the pre-implantation stage as Hartley documented), which is thought to be a kind of ‘keep your cards hidden until the last minute’ strategy. In addition, there is some evidence to suggest a behavioural mechanism that could reduce subordinate breeding and, in his 1987 book, Running with the Fox, David Macdonald noted that the dog in his captive social group was only interested in the dominant vixen (called Niff) during the breeding season, despite the subordinates ‘flirting’ with him. Macdonald also found that when he removed the dominant pair and introduced an un-related dog fox stranger, only Niff’s eldest daughter -- who was barren for five years under her mother’s matriarchy -- mated and produced cubs. This implies that dogs are only attracted to the dominant vixen in a group. Assuming this is representative of the wild, subordinate matings within a social group presumably occur away from the group, where the dog is less able to assess social rank. Despite all of the foregoing, it is not unknown for subordinates to produce litters, particularly in urban areas; the cubs may subsequently be killed by the dominant vixen (infanticide) or the other litter(s) may be raised independently or combined with the dominant vixen’s cubs and raised together.

Whatever the full picture may turn out to be, the number of non-breeding (sometimes called “barren” or, archaically, “dry” owing to their failure to produce milk) vixens in a population is highly variable. In ideal conditions (i.e. sufficient food and low fox density), some 80% to 100% of vixens will breed, while only around 30% may breed in unfavourable years. In rural Oxford, where mortality was low, Macdonald found that around 60% of vixens were barren, compared with the 24% Stephen Harris found in London, the 20% Cavallini and Santini recorded in Italy and the 8.5% Nicola Marlow and her colleagues found in Western Australia. Elsewhere in Europe and in the USA, where foxes are heavily trapped for fur and as rabies control, only around 10% will be barren. There is also variability associated with age – older vixens are more likely to breed than younger ones (in some studies, about 50% of yearlings breed in any given year compared with 90% or more mature vixens). As Macdonald pointed to in his book, the importance of the interaction between food, territoriality and social behaviour cannot be under-estimated and explains why the proportions of breeding and barren vixens, and litter size, change between years and in different habitats. In essence, food controls territory, which in turn regulates sociality and thus determines the number of breeding vixens in an area.

Finally, disease can interfere with fox reproduction. During their extensive study on the impact sarcoptic mange had on Bristol’s urban fox population, Carl Soulsbury and his colleagues found that females with advanced mange didn’t breed, while severely infected males failed to undergo spermatogenesis (i.e. they didn’t produce any viable sperm). (Back to Menu)

Red foxes in copulatory tie
Following successful ejaculation, a bulb at the end of the dog fox's penis engorges with blood and causes the pair to temporarily lock together - this is known as a copulatory tie. The tie can last anywhere from a few minutes to and hour-or-so.

Mating and monogamy
In his contribution to the 1975 compendium The Wild Canids, renowned behaviourist Mike Fox classified the canids into three groups, based on their breeding system. Fox considered Vulpes to be ‘Type 1’ canids based on them being temporarily monogamous – i.e. the pair separate after the young have reached independence. Historically, however, it was long considered that foxes were entirely monogamous and, in his 1952 book, British Mammals, L. Harrison Matthews wrote:

The male is monogamous and usually mates only once with his vixen; should his mate be killed he usually refuses to take another, forming an example of faithfulness unknown in other wild animals.”

Monogamy is generally rare among the mammals and, in the vast majority of cases, it is actually social monogamy that is seen – i.e. a new partner will be accepted following the death of the previous one. The situation in foxes is rather complex and, as we shall see, the presence of monogamy or promiscuity is largely based on resource availability and population density. Initially at least, foxes do appear monogamous in that they tend to live in pairs (or small family groups) and the dominant male will mate with the dominant female. This pair-bond seems to last for life, although high mortality in some populations can mean that some 80% of the breeding population may be comprised of new pairings, owing to the death of one partner. There are reports of apparently strong emotional attachments between the pair, and Macdonald recounted a curious ‘mourning’ behaviour in a dog fox after his mate and cubs were killed when the earth was dug out and gassed; he wandered almost the entire territory boundary barking periodically with the staccato ‘wow-wow-wow’ call so familiar among foxes. I shall return to the topic of monogamy shortly, but shall first cover the process leading up to copulation.

As mentioned, the vixen comes into oestrous for around three weeks during the winter and, for between one and six days of this period (estrus), she is receptive to being mated by the dog. Consequently, the dog frequently ‘mate guards’ during these few weeks – the dog and vixen sleep, travel, and even hunt together (usually with the dog trailing the vixen) and as the vixen approaches estrus she may permit mating attempts by the dog. In some cases, more than one male may court the attentions of a single female and there is a report from Pogonno-Losinoe Island reserve in Moscow of four males pursuing a single vixen. David Macdonald observed that, as the vixen approaches estrus, the male follows as close as the vixen will allow, holding his brush “ram-rod straight”, urinating on every object he passes and showing no discernable interest in food. The dog will also closely investigate any scent marks that the female leaves and an unpaired female will scent-mark frequently while in oestrous. In her 2001 book, The Blood is Wild, Bridget MacCaskill described the behaviour of her hand-reared vixen on a walk during her first breeding season:

She pulled me along as if we could not get anywhere fast enough, leaving her mark everywhere, on pathways, patches of moss, flat-topped boulders, and generally making sure the fox world knew she wanted a mate.”

Early attempts by the dog to mount the vixen tend to be rebuked with much gekkering and snickering from the vixen, but when she is receptive she will allow the dog to mount her and the pair will mate – they may mate several times during her estrus. Just prior to, and during, mating there is often much vocalisation (in the form of short wails and shrieks) from both parties and submissive posturing (see: Behaviour and Sociality) by the vixen may proceed copulation. Indeed, one of the best descriptions of fox mating I have come across is given by MacCaskill, who described the behaviour before, during and after her vixen (called Rusty) mated with a stranger. From her vantage point in a tree on a bitterly cold winter’s night, MacCaskill observed:

There were squeals of excitement as they met and rapid chitterings as they rose together on hindlegs to box and bite. The dog played eager, sniffing her hindquarters. Submissive, and uttering chirruping sounds of invitation, Rusty rolled over to display her pale grey underparts. She teased him, flirted with him, led him on, all the time her eyes assessing what he would do next. Twice she stood for him, apparently willing, but each time his paw came on to her flank, she snarled and wriggled away. Preliminaries over, the vixen sauntered away, pretending indifference. The dog, eager and panting, followed at once. The vixen squatted to leave her mark. The dog barged her aside to sniff, scrape, and sniff again. More chirruping sounds from the vixen. Just as I was beginning to wonder if they ever would mate, she suddenly stood and allowed the dog to mount. The act was no different to any other we had seen – a submissive vixen, a dog who knew instinctively what he must do, and a painful locking together, judging by the screams of rage from the vixen.

Red fox familyCopulation lasts only a few seconds and, following ejaculation, the pair are locked together -- a ‘copulatory lock’-- for up to 90 minutes (above), owing to contraction of the vixen’s vagina and the swelling of the bulbus glandis tissue at the tip of the dog fox’s baculum described earlier. Unsuccessful mounts (i.e. those that don’t end in ejaculation), and there may be several in a single mating session, do not appear to result in locking. Indeed, successful (i.e. locking) matings often appear to be preceded by several 'thrust' mounts, and this thrusting behaviour may be a necessary prelude to ejaculation. The copulatory lock evolved as a method of providing the best possible chance of fertilization, by preventing other males from mating with the vixen during this time (thereby giving the dog’s sperm a time advantage over that of any competitors). Once locked the dog will lift his back leg over the vixen’s back and the two will stand back-to-back: an evolutionary mechanism to allow them to defend themselves from any potential predators. This lock is apparently very strong and I have come across one (admittedly unverified) account of a lady who came out into her back garden and yelled at two locked foxes, at which point one took off over a wall, dragging the other behind it!  Curiously, in his 1999 book, Battle of the Sexes, John Sparks mentions copulatory plugs in foxes. Copulatory plugs are small jelly-like blockages that males implant in the vagina of a female with which they have just mated in a bid to prevent her mating with anyone else. It is well known among some animal groups (particularly rodents), but Sparks writes:

In the case of foxes and of eastern grey squirrels in the USA, the females foil the males’ attempts to enforce further chastity by removing the rubbery copulation plugs themselves within seconds of mating…”

While this is certainly true of squirrels, I have been unable to find any further reference to this phenomenon among foxes – it seems to me that the copulatory lock is essentially the male making himself a copulatory plug. Moreover, given that a male may mate with the same female several times during her estrus, it seems unlikely he would employ a plug that would make the process more difficult for himself later on. MacCaskill went on to describe how, after about 30 minutes, the pair unlocked and stood together stretching and yawning before curling up together and going to sleep.

I have mentioned that foxes often appear to pair for life, but this doesn’t assume monogamy. Indeed, once the female is no longer in estrus, the dog fox may leave her, usually only temporarily, to seek out additional mating opportunities. Tracking studies in Bristol, for example, have revealed that, after the dominant vixen has ended her estrus, the male often rapidly expands his range -- in many instances more than doubling the distance over which he travels -- to increase the likelihood of encountering other receptive vixens. During these reproductive movements it seems that the foxes actively intrude into the core areas of neighbouring territory (quite the opposite pattern to that seen when foxes disperse – see Q/A). One study by the Bristol University team found that these ‘mate searches’ occur mainly during January and February, with the bulk (just over 70%) happening in the second half of January. Similarly, the Bristol mammalogists have found that, as vixens approach estrus they will often spend more time at the periphery of their range; this presumably puts them in contact with more males than if they remained in their core area. Foxes are very vocal during this time (see Behaviour and Sociality) and these calls seem to be employed to help them find each other, reducing the time spent searching. Intrusion into the core areas of other foxes invariably leads to increased confrontation and thus the potential for fights. Correspondingly, the peak period for male mortality is January and February as they are either killed in fights competing for access to females (bite wound frequencies increase at this time of year) or run-over during their long-range movements. In addition, the male foxes do not appear to eat during these reproductive movements and hence lose body condition.

So, despite initial perceptions that foxes are entirely monogamous, it seems the picture is more complicated. Indeed, the picture painted by tracking studies has recently been corroborated by genetic data. A study by Bristol University published in the journal Behavioural Ecology during 2004, revealed mixed paternity in urban fox litters. Monogamy was observed or assumed in only about half of all breeding attempts; it was common for females to be mated by more than one dog (polyandry) and for males to mate with more than one vixen (polygyny). When looking at litters of known paternity, 16 litters (38%) were found to be the product of more than one father, while the number increased to 20 (69%) when the litters of unknown paternity were included in the analysis. On average each litter was the product of two fathers, although anywhere up to seven different males may have been responsible for siring a single litter. More interesting still was the observation that, of the 30 litters for which paternity could be determined, only six (20%) were sired by males from the same social group. It transpired that, although both dominant and subordinate vixens mated with males within their social group, the majority of cubs produced by subordinate females were sired by males outside their group.  Dominant and subordinate females produced cubs with dominant and subordinate males from other social groups, but dominant vixens didn't produce cubs with subordinate males from their group. Dominant individuals of both sexes reproduced at every breeding opportunity, while the subordinate individuals only did so 40% (males) or 56% (females) of the time. Incest (i.e. mating with one's kin) was observed, but such occurrences are considered rare.

Interestingly, food may also play a role in this promiscuity. A study on Arctic foxes (Vulpes lagopus) by Cassandra Cameron and colleagues at the Université du Québec à Rimouski in Canada, published in Behavioural Ecology during 2011, reports that extra-pair matings were more common where food is abundant, with foxes being more prone to monogamy in areas where food is scarce. A similar observation was made by Cynthia Zabel and Spencer Taggart among the Red foxes of Round Island, Alaska during the early 1980s. In a paper to Animal Behaviour during 1989, Zabel and Taggart report that polygyny occurred among the foxes, correlated with abundant food (i.e. dogs would mate with more than one vixen when there was lots of food) but, when there was a widespread nesting failure of seabirds on the island as a result of the 1982 El Niño in the Bering Sea, the groups became monogamous (only one vixen bred in each group). The suggestion is that when resources are abundant the females have little to lose by sharing a male, but when times are tough it pays to have someone to help with securing limited resources and putting food on the table. In addition, when food is plentiful more vixens are likely to ovulate so males presumably have a greater choice of potential mates than when food is scarce.

Vixen with playing cubs

The advantage of polygyny for the dog fox is that he spreads his genes around. Considering that many (especially subordinate) males will only live long enough to breed once or twice, spreading the cubs around helps to ensure that at least some of them survive to pass on their genes. For instance, if the dominant vixen was to die before giving birth, a monogamous dog fox would have to wait a year before he could mate again. For the female, polyandry helps ensure that her litter has the best possible selection of genes to help them survive whatever life throws at them. At the same time, it seems that a dog fox can be ‘duped’ into helping raise the litter even though only some of the cubs may be his. Indeed, the Bristol team observed that dominant males continued to provide food for the dominant vixen and her cubs, despite some of the cubs being the progeny of a rival male. This suggests that male foxes are unable to discriminate between the cubs that are theirs and those which aren't.  The culmination of this observed polyandry seems to be linked to the patrimony of fox territory. It is not uncommon for successive generations to inherit the territories on which they were born, so the observed promiscuity is probably a strategy to counteract the problems that would arise from inbreeding (i.e. mating within the family group).

Finally, it has often been assumed that urban and rural foxes are distinct entities – I have even heard arguments that they should be considered different subspecies! This does not appear to be the case and urban and rural foxes intermix in both their territory use and breeding. During the early 2000s, for example, Peter Wandeler and his colleagues found that the foxes living in the Swiss city of Zurich interbred freely with those living in peripheral rural areas. Wandeler and his team did find a small tendency for urban foxes to breed preferentially with other urban animals and rural animals with other rural animals (probably more out of convenience than active desire), but overall the urban and rural populations were genetically only about 4% different from each other. (Back to Menu)

Gestation, birth and litter size
Fox uterus showing placental scarsMost successful matings will occur during late January or early February and, following successful fertilization, implantation occurs in the following 10 to 14 days (average is 12 days after fertilization), when progesterone levels are at their peak. Assuming successful implantation, the vixen will begin a gestation (pregnancy) that can last between 49 and 58 days; typically, Red foxes gestate for 52 days (around 7.5 weeks or just under two months). According to Mark Cardwine, in his 2007 Animal Records book, Red foxes have the shortest gestation of the dogs – domestic dogs, by comparison, gestate for 58 to 65 days, African wild dogs (Lycaon pictus) for 69 to 73 days and Bat-eared foxes (Otocyon megalotis) for between 60 and 75 days. Foetuses can be lost at any time between conception and birth and, if this happens, they are then re-absorbed; this is a normal part of fox (indeed mammal) reproductive biology. In Wales, Huw Gwyn Lloyd found that an average of about 10% of pregnancies didn’t make it to term, although in some years this reached 22% while in others losses were negligible. We can get an indication of how many foetuses make it to term and how many are resorbed by looking at the vixen’s uterus. Like most mammals, foxes form a placental connection to their young and these connections to the uterus leave their marks. Indeed, since at least the 1930s we have known that scars on the uterus lining can be used to estimate successful births in mammals. The technique has been used in foxes since at least 1949, when New York biologist William Sheldon used the technique on American Red and Gray foxes (Urocyon cinereoargenteus).

In a 2000 publication for the Game and Wildlife Conservation Trust, Jonathan Reynolds summarised the topic of placental scar counting in Red foxes. Reynolds described how, post-mortem, the scars on the uterus -- each of which signify the site of a developing foetus -- can be used to assess litter size. Dark scars are left by the placenta once it has disconnected from the uterus and indicates a successful birth; immune cells called macrophages migrate to the disconnection site and begin breaking down the blood, leaving haemosiderin and lipids, which give the scar its colour. If the foetus is resorbed all that persists is a faint (pale) scar on the uterus marking its position. In theory, counting the number of dark and light scars on a uterus should tell you how many ova successfully implanted and the number that made it to birth. In practice, however, this requires practise and it can often be difficult to distinguish aborted foetuses from the scars from the previous year’s births (which fade in time and may persist for longer than traditionally believed). Such counts can also overestimate litter size because it cannot distinguish live and still births, or between births and very late-term abortions. It can, nonetheless, often be used to good effect and, in 1970, Jan Englund developed a greyscale scale (with six shades) to distinguish active (birth) from old (previous births) or resorbed scars. Over subsequent years, various authors have improved upon the method and, in 2011, French biologists Sandrine Ruette and Michel Albaret published an improved method that involved staining the scars. With this they were able to positively identify scars relating to successful births (and less ambiguously than using a colour card), but couldn’t separate previous births from abortions. In the end, it is the number of young born that interest those involved in fox conservation and management and hence such methods are aimed at addressing this. (Photo: The prepared uterus of a Red fox vixen showing 12 dark scars and a single light one,implying she successfully gave birth to 12 cubs. Photo courtesy of Dr Jonathan Reynolds at the Game Conservation and Wildlife Trust.)

In his fascinating 2000 book, My Life with Foxes, the late New Forest naturalist Eric Ashby described how the signs of pregnancy are not immediately obvious in vixens, with the size and shape of the mother being only slightly altered by the tiny unborn cubs. It seems that the first indication is an increase in appetite, followed by the fur around the teats becoming bare as they swell and change from their pale colour to be bright pink and prominent. Assuming all’s well, the vixen’s mammary glands emerge about two weeks before the young are due to be born and, at around the same time (late February), the vixen becomes extremely secretive as she starts looking for an earth in which to give birth (a natal earth). She may dig a new earth, or use a previous one – underneath sheds and out-buildings are popular natal earth sites, as are sites under gravestones (see Dens/Earths). In most habitats, the only period during which a den is almost essential is the breeding season. In some cases a fox will give birth above ground in the trunk of a fallen tree, a tussock of grass or in a log pile, but such instances are rare. Where an ‘al fresco’ birth does happen it may have been that the vixen was forced to leave the earth for some reason and ‘caught short’. Indeed, in Running with the Fox, David Macdonald described finding five mole-grey newborn foxes nestled cosily in a dry tussock of reeds bordering a duck pond. Later that night, having disturbed the vixen, Macdonald watched her move the youngsters to a nearby earth under an oak tree. Most foxes, it seems, are born underground. In the days leading up to and following birth, the vixen is typically sustained by food brought to her by the father and, in some instances (as we’ll come on to shortly), subordinate vixens in the social group. The vixen generally does not allow the dog access to the young while they remain in the earth (the first sight he apparently gets is when they appear above ground) and he leaves food at the entrance. No scats will be deposited in the vicinity of the earth during this time.

Fox cub quintetThe largest unconfirmed litter I have come across is 14 young -- called cubs, kits or pups -- while there is a confirmed case of a vixen from Tippecanoe County in Indiana having 13 cubs, although the mixing/pooling of the litters of two or more vixens in a social group probably account for many such large counts. Vixens typically have four pairs (eight) of mammae (nipples), although as many as 10 have been reported, each with eight to 20 lactiferous (milk-secreting) ducts. In a recent article to BBC Wildlife Magazine, Stephen Harris notes that the teats in the groin produce more milk (presumably have a greater number of lactiferous ducts) than those farther forward. According to Lloyd in his 1980 opus The Red Fox:

“It is certain, however, that the wild fox cannot successfully nurse a litter of more than about ten cubs unaided…”

Indeed, the average litter contains four to six cubs, with eight being the largest that a single vixen in the UK is likely to produce. Interestingly, litter size is relatively constant across years and it seems that even where foxes are heavily controlled (causing a reduction in the population density) the population responds by increasing the number of vixens breeding, rather than by increasing the number of cubs in the litters. This makes sense when we consider that culling reduces density and increases the number of available territories, meaning it is easier for a fox to strike out on its own and free herself from the breeding suppression imposed by her mother. Hence, more vixens have litters, while litter size itself is correlated with the physical size (not necessarily weight) of the vixen, which is independent of available territory. That said, there are some data to suggest that the number of cubs in the litter can also vary according to habitat. Experiments by a group of scientists based in Spain, for example, found that foxes in the “vegas” (their term for favourable habitat) had larger litter sizes than those in the “steppe” (less favourable habitat).  The vegas population also had a higher number of barren vixens than the steppe -- 19.3% and 1.7%, respectively -- which presumably reflects breeding suppression by dominant vixens in favourable habitat. Similarly, an outbreak of rabbit haemorrhagic disease in Spain during 1988 caused a substantial (90%) decline in rabbit numbers -- the staple food of these foxes -- and caused a decline in the average litter size that ultimately led to a reduction in fox abundance.

Interestingly, habitat quality doesn't only impact the number of breeding vixens on a territory; it can also influence the sex ratio of the litter and this, in turn, can affect the date the cubs are born. We now know that mothers invest more energy producing males than females and vixens living in high quality habitat tend to be larger than those in poorer areas, putting them in a better position to cope with the higher energetic demands of male cubs: these individuals thus tend to produce more male cubs (although they don't have larger litters), while smaller vixens tend to produce more female cubs. For many years we have known that male cubs are typically born larger than vixens (dogs were 11.4% heavier than vixens in one study of Welsh 45 litters by Huw Lloyd), which implies that even in the womb the mothers are feeding their male cubs more than female ones. During his studies of foxes in Wales, Lloyd also recorded an interesting shift towards male cubs as gestation progressed. Lloyd looked at the sex ratio of 333 embryos from 68 litters and found that early in gestation the sex ratio was slightly female biased (with 48.9% being male), but by the time the mothers were 40 days from giving birth the ratio had shifted slightly in favour of males (51.5%). This shift isn't huge (only 2.6%), but it does suggest that male embryos have a higher survival rate than female ones; in an article to the July 2012 issue of BBC Wildlife Magazine, Stephen Harris goes a bit further, suggesting that vixens may preferentially abort female embryos. Recent work at Bristol University by Helen Whiteside has found that the number of males in the litter also has a bearing on when the vixen gives birth. Logically, you could be forgiven for expecting that litters with more dogs than vixens should be born earlier, allowing more time for the male cubs to grow and prosper, but quite the opposite is observed, as Harris explained in the aforementioned article. During her Ph.D studies, Whiteside found that male-dominated litters were born later than vixen-dominated ones; this allows the cubs to be weaned at the point that their main prey (rabbits and voles) start breeding and should thus mean an abundance of solid food for them. If the cubs are born early, they're weaned before this mammal 'glut' and are more dependent on earthworms and insects in the interim, which are less predictable.  If it is a hot, dry summer these invertebrates are difficult to find and this can severely impact the growth of the cub. Cubs reach their adult size by the autumn, so they can't 'make up' for any growing lost through a dry summer and, thus, having a bountiful supply of young mammals to fall back on can make all the difference. Male cubs, it seems, grow faster than females both when suckling and when weaned on to solid food. Why should this be important? As we'll see later, size is important for males (larger cubs become larger adults that are more likely to find and keep a territory and thus more likely to father more cubs than smaller males). For females, size doesn't have the same implications in later life and a small vixen is just as likely to breed as a larger one.

The peak time for births in the UK is mid-March, although cubs can be born any time from late January until well into April. There are even a few very early records. Brian Vezey-Fitzgerald, for example, recorded fox cubs above ground in his garden on 5th January 1963, during the very harsh winter with thick snow cover; working backwards, this suggests they were born in early December and that the was vixen fertilized in October. In his book, Town Fox, Country Fox, Vezey-Fitzgerald went on to describe how there was more variation in cub births in Europe:

“… in France and Belgium, births of wild fox cubs have been recorded in every month of the year except August: even births in June and July are not regarded as altogether exceptional.

In the UK, the latest litters tend to be born during April and, given the spontaneous nature of the Red fox’s breeding biology, I generally treat unverified reports of very late fox cubs with considerable suspicion. That said, a fox cub estimated to be only three-weeks-old was taken in by South Essex Wildlife Hospital on 19th November 2013, after it was found in central London with no earth in sight. This represents that latest verified UK birth I have come across and, working backwards, suggests birth during the last week of October and successful mating around the 9th September. I would be very interested to hear from readers who have evidence of very early or late fox litters. In Australia, where seasons are reversed compared with the northern hemisphere, most mating occurs during June and July and fox cubs are typically born during August and September. (Back to Menu)

Growth and development of the cubs
Four-week-old fox cubsAt birth, the cubs are covered in a fine grey woolly fur, have a pink nose (which turns black within the first week), weigh between 50 and 150 grams (1.8 – 5.3 oz.) and are blind and deaf. Like those of most mammals, fox kidneys excrete urea directly into the amniotic fluid during development; this could damage the foetus's delicate corneas and thus the eyes remain closed until after birth. In their detailed study of the development of 160 Red fox foetuses, American biologists James Layne and Warren McKeon found that the average birth weight was 100 grams (3.5 oz.), with a head 41 mm (just over 1.5 in.) long and a tail measuring around 57 mm (just under 2.5 in.) in length. The cubs are reasonably well furred, although the hair is short -- 6 to 8 mm (one-third of an inch) on the back and head, 5 mm (about one-fifth of an inch) on the stomach and much shorter on the muzzle, chin and lower legs -- and many will have a white tip to the tail, with hairs of 2 to 3 mm (one-tenth of an inch) in length. At birth, the fur is chocolate brown in colour in ‘red’ and ‘cross’ morphs and jet black in silver/melanistic animals. Layne and McKeon observed that the sex of the cub was readily determinable at birth. Indeed, the anatomists found that vixens and dogs could be sexed about two-and-a-half weeks before birth, based on the distance between the genital openings; external genitalia were visible about 38 days into gestation (i.e. two weeks before birth).

Newborn cubs are unable to thermoregulate (maintain their body temperature) fully for the first two-or-three weeks; they must huddle together and, in the early stages, stay close to the vixen to prevent hypothermia. Indeed, during the first two or three days, the vixen will not leave the cubs (even to drink); she stays in the earth and acts as their 'thermal blanket', until their fur has grown sufficiently to provide some insulation – observations from captive foxes suggest that by about a week old the fur has grown sufficiently for the cubs to thermoregulate well enough to be left alone briefly. At this point the vixen will leave them for short periods (typically only a few minutes) to drink. The cubs’ eyes and ears open at between 10 and 14 days old and teeth begin appearing in the upper jaw (a couple of days later for bottom jaw teeth). By around two weeks old, the fur has changed from dark grey to a chocolate brown colour and by three weeks (above) the black eye streak appears; the white muzzle and some red patches are apparent by four weeks old, as the ears become erect and the muzzle starts to elongate. At about six weeks old the coat is a similar colour to that of the adult, but still retains its ‘woolly’ cub-like appearance – the woolly fur is covered by longer guard hairs (giving a shiny lustre to the coat) at about eight weeks of age.

The cubs, like most mammals, are born with (initially cloudy) blue eyes.  Eye colour is a result of pigment, typically although not exclusively eumelanin, deposited in the iris and, essentially, the more you have the darker your eyes appear.  At birth, our irises have only a small amount of eumelanin, which allows the scattering of short wavelength (blue) light more than long wavelength (red) light, causing our eyes to appear blue (this is known as the Tyndall Effect).  Eumelanin absorbs light, so the more you have, the less light gets scattered and the darker the eyes appear.  Melanin production increases during the first few weeks of life so, at birth, we (and many mammals) have blue eyes, which change to their adult colouration shortly afterwards.  Fox cubs are born with slaty-blue eyes that change to amber (thought to be a result of a carotenoid pigment called lipochrome) at four or five weeks old.

For several weeks after the birth of the cubs, the vixen's maternal duties involve playing and napping with the cubs, grooming them (paying special attention to the groin and ears) and eating their waste products. Indeed, according to Ashby’s descriptions, the vixen will keep the earth spotlessly clean and, even as they get older, the cubs are apparently reluctant to soil the earth. The cubs are unable to evacuate their own bowels until they’re about two weeks old (again, based on captive animals) and without this stimulation they will retain the waste products and this can prove fatal. This is a well known phenomenon in mammals and studies on rats suggest that the neural mechanisms controlling bladder emptying undergo marked changes during the first three weeks of life. The bladder and bowel are voided when a nerve response called the perigenital-bladder reflex is stimulated; the young cannot do this themselves until the spinal mechanisms that control it have developed sufficiently. It seems that, up until about three weeks (in rats) the mother licking the genital and rectal area (collectively referred to as the perineum) acts to stimulate this reflex. According to David Macdonald in his book, Running with the Fox, this toileting is carried out every two hours for the first week of the cub’s life. The vixen may also spend a considerable time grooming the fine fur of newborn cubs, although this is apparently not essential.

Fox cubs are lactophagus (dependent on their mother’s milk) for the first four-to-five weeks of life. A vixen with an average litter will be producing about 300 mL (about half-a-pint) of milk per day when the cubs are around three days old, increasing to 800 mL (about 1.5 pints) per day by the time the cubs reach 16 days old and, by the time the cubs are weaned, she will have lost 20% to 30% of her body weight. The milk is high in protein (about 32%) and sugar (25%) but slightly lower in fat (18%), allowing the cubs to build muscle quickly. Indeed, the graph below shows the average rate of cub growth and illustrates how males overtake females at about four weeks old. The deciduous (milk) teeth are complete at six-to-seven weeks old (allowing the cub to take solid food), but the vixen may start presenting the cubs with solid food from about three weeks old, even though they are only able to suck the juices and play with it (helping to develop jaw muscles and hunting technique). The first solid food seen by most cubs is meat regurgitated by the vixen. Indeed, the vixen may start regurgitating food for the cubs around the time they’re three weeks old and, although the striated muscle lining a fox’s oesophagous is under nervous control (allowing them to regurgitate voluntarily), as in most canids the regurgitation is usually stimulated by the cubs licking the corner of the adult’s mouth. To the best of my knowledge, the mechanism triggered by this licking is unknown, but Charles Horn -- Associate Professor of Medicine and Anaesthesiology at the Hillman Cancer Center in Pittsburgh, USA -- suggested to me that licking might stimulate the trigeminal nerve in the face, which subsequently triggers the regurgitation.

Fox Cub Growth Graph
The average growth of male and female fox cubs, taken from various sources including data provided by Vale Wildlife Rescue.

In a paper published in Comparative Biochemistry and Physiology during 2000, Øystein Ahlstrøm and Søren Wamberg at the Agricultural University of Norway reported on the milk intake of captive fox cubs. A vixen starts producing milk around the time the cubs are born and these researchers found that the daily intake per unit of body mass was around 30 grams (1 oz.) of milk per 100 grams (3.5 oz.) of cub. In practice this meant that, depending on the size of the cub, they were drinking anywhere between 31 and almost 200 grams (up to 7 oz.) of milk per day. The total milk yield amounted to between 200 and 300 mL per vixen two or three days after the cubs were born; this increased to about 800 mL by the time the cubs were about two weeks old. Overall, Ahlstrøm and Wamberg found that a vixen’s daily milk production depended partly on the number of cubs in the litter, but more closely on the total body mass of the litter. The vixen’s milk is high in energy and, during the first month of life, the cubs will put on 15 to 20 grams (up to about two-thirds of an ounce) per day in weight. By around six weeks old the cub will weigh just over a kilogram (just under 2.5 lbs) and by about 4.5 months old it will reach its adult body size but, at around three kilograms (just over 6.5 lbs), not its adult weight. Some cubs will grow faster than others -- growth rate is determined by access to food and some members of the litter will monopolize food -- and this can give the false impression of mixed litters (although this phenomenon is not unknown and, in Bristol, up to three litters have been found mixed into a single ‘crèche’).

Vixen suckling cubsVixen suckling cubs
Cubs will start fighting for scraps of meat in the earth almost as soon as their eyes open, but they derive all their nutrition from milk until they're about five weeks old, although they may continue to suckle in between consuming solids for several weeks.

The dog fox, and in some cases non-breeding ‘helper’ vixens (see: Behaviour and Sociality), will hunt for food to sustain the vixen and the cubs until the cubs are sufficiently independent to be left for longer periods (around six weeks old); the vixen will then resume hunting for herself and the cubs. That said, there appears to be some disparity between the behaviour of the dog fox in different regions and this has led several authors to consider that dog foxes are rather disinterested fathers. Roger Burrows in his book, Wild Fox, for example, saw no evidence that the dogs paid any interest in their young and neither hunted for them nor played with them. Conversely, however, in his 1962 booklet, Henry G. Hurrell described watching a dog fox catch a rabbit and immediately take it to his family waiting on a nearby hillside, passing it to the vixen who then gave it to a cub. Similarly, MacCaskill noted how the dog fox she was watching in the Highlands of Scotland took an active role in hunting for the family; on one occasion, upon returning to the earth with a hare, the dog fox had it ‘snatched rudely’ from him by the vixen. So, for the most part, it seems that dogs do play at least some role in provisioning for the cubs, although how much physical contact they have with them is less clear. There are some reports of fathers playing with (or perhaps more accurately being played with by) the cubs, but generally it seems they spend little time with them. Indeed, the dog rarely spends any time in the earth, although Harris and his colleagues in Bristol found that, occasionally, one or even two dogs may remain in the earth with the cubs. Several observations, including those by Valeria Vergara in Canada, suggest that the main role of the dog is providing food and defending the cubs – Vergara found that males spent almost twice as long involved in ‘vigilant behaviour’ (i.e. keeping a look out for danger) as vixens. In addition, in his 1906 book, The Fox, Thomas Dale was convinced that the dog was a devoted father:

Should the vixen meet her fate while the cubs are small, their father nobly takes charge of them, carrying them perhaps to some safer locality, and caring for them in the best way he knows.

During her studies in Ontario, Canada, Trent University biologist Valeria Vergara observed eight Red fox families and noted that the male’s job appeared to be more involved with providing food to the cubs and scanning the vicinity for signs of danger. Vergara found that, in general, the dogs contributed less direct care (i.e. spent less time socialising with the cubs) than the females; overall, the percentage of their time spent attending to the cubs was about 28% and 16%, for vixens and dogs respectively.

If disturbed, the vixen may move her cubs to an alternative earth within her territory and, in The Red Fox, Lloyd told how some countrymen were convinced that the litter is split (some maintain by sex) at six-to-eight weeks and kept separately. Lloyd knew of no evidence to support this, but considered it possible. Very young foxes are carried by the vixen in a similar manner to a kitten – hanging by the scruff of the neck from the vixen’s mouth. In urban settings, adults will often bring a range of toys (balls, dog chews, shoes, etc.) back to the earth for the cubs to play with.

Vixen with cubsThe vixen may continue to lactate until around the twelfth week, but cubs are fully weaned by six to eight weeks old (about May time) and, at this point, food is provided by both parents (and often any 'helpers'). As the date of weaning approaches, captive individuals have been observed burying food for their cubs to find, although studies in the wild often fail to find any sign of this. The cubs emerge from the natal earth at about five weeks old and may be seen playing outside in late April or early May; for the next few weeks they will contain their activity to within view of the earth. By the time the cubs are eight or nine weeks old they have usually abandoned the earth altogether, opting instead to lie-up above ground in nearby dense vegetation (bramble, for example); they’re now also ranging more widely, using most of the territory. The cubs can be easy to watch until they reach about ten weeks old, at which point they can be very neophobic (cautious of unfamiliar objects) and appear to trust only those with whom they have grown up. This may, however, vary from fox to fox and Hurrell observed that there were wide individual differences in a fox’s reaction to danger – some being ‘wilder’ than others.

The adults will continue to bring the cubs food until they’re about four months old, by which time their adult dentition is largely complete and they’re capable of providing some food for themselves, although they still lack the hunting proficiency to catch birds and mammals and their diet is heavily based on fruits and invertebrates. It seems that as time progresses, the cubs split into smaller and smaller groups as they begin to forage on their own during August, and will be full-grown by the end of September; their winter coat begins growing during August and is complete by the end of December. The juvenile foxes will reach sexual maturity at nine or ten months old. In low density populations vixens will often breed in their first year -- although this is not always the case (just over half the vixens in one of Stephen Harris’ London studies failed to breed in their first year) and they’re generally more prone to abortion than older females -- but most dogs won’t breed until their second year. Generally, foxes are considered cubs up until they’re four months old, after which they’re juveniles and, once they reach one year old they’re considered adults.

Once the cubs are independent they may either leave the group and search for their own territory -- more common among males -- or remain on the territory with their parents as long as resources allow. Based on the tracking studies undertaken in Bristol, dispersing during the first winter doesn’t improve a dog fox’s chance of breeding. This subject is covered in more detail in the associated Q/A. (Back to Menu)

Red fox huntingBehaviour and Social Structure: In her 1912 children’s book, The Tale of Mr Tod, Beatrix Potter described the fox as being “of a wandering habit” and having “half a dozen houses but was seldom at home”. Indeed, Potter’s view that foxes were solitary antisocial roamers was widely held among the scientific community until, in the early 1970s, Professors David Macdonald and Stephen Harris began their studies on the foxes of Oxford and London, respectively.  During the last four decades, we have learnt a great deal about the social life of the Red fox. We now know that to be solitary does not mean to have no social life.  In the following summary I will draw extensively on the observations of Oxford University zoologist David Macdonald and Canadian naturalist Dr J. David Henry. These scholars have contributed hugely to our understanding of fox behaviour and, while I hope to do their decades of research some justice here, for much more in-depth and fascinating coverage of this subject I refer the reader to Macdonald’s 1987 book Running with the Fox and Henry’s 1993 book How to Spot a Fox. In conjunction with the work carried out by Macdonald and Henry, I have also drawn on some of the observations and experiences of veteran fox watcher and fox rehabilitator Mike Towler who has, through his years of interacting with foxes (indeed, various animals) gained some fascinating insights into fox behaviour and how they interpret the world around them.

Foxes are predominantly solitary canids. That is to say that, throughout most of their range, Red foxes live either individually or in pairs. Most of us are familiar with the fox family groups shown on TV programmes, such as the BBC’s SpringWatch, but this is actually a rather uncommon occurrence outside Britain’s towns and cities. Even where a pair of foxes live on a territory, they will typically spend the majority of their active time apart; some will only come together during the breeding and cub-rearing seasons. So, why should this be? After all, other canids (wolves being a well known example) routinely live in social groups, so why not foxes? The answer is relatively simple: food. As we have already seen (see: Food and Feeding), the Red fox evolved to hunt small and medium-sized mammals and birds – essentially, these are meals for one. Wolves, by comparison, work as a team to bring down large prey that can feed the pack for several days. A single wolf could not bring down an elk, just as a vole or blackbird couldn’t feed more than one adult fox. Thus, wolves have a need for cooperation (and hence sociality), while foxes do not. Indeed, when you’re looking for bite-sized meals, having more than one fox around is unwanted competition, rather than essential assistance. As we shall see, however, there are other advantages (more than just securing a big meal) to having other members of your species hanging around, but these are typically of secondary importance to being able to feed yourself. The question, then, is what happens to allow the formation of the fox social groups? (Back to Menu)

Live and let live: the evolution of group-living
If foxes have evolved to hunt solitarily for small prey, why do we sometimes find them living in groups? Do they hunt in packs for larger prey? The answer to the latter question is no: despite some Internet and media stories to the contrary, even where foxes live in social groups, they do not hunt in packs. There are, however, very occasional reports of cooperation between foxes. Australian biologist Alan Newsome, for example, reported a dog and vixen working together to catch large rabbits. In addition, during February 2010 I received a fascinating e-mail from a keeper in the hills of Northern Ireland. The gentleman described how he came across two adult foxes attacking a mature ewe with a prolapsed uterus.

Despite the lack of pack-associated hunting in foxes, the answer to how group-living arose does, nonetheless, seem to involve resources and, more specifically, an abundance of resources. Professor David Macdonald spent a great deal of his time pondering the question of how group-living evolved in Red foxes. He noticed that, generally speaking, food is unevenly distributed within a given area (territory) and its availability varies ephemerally; from night to night, season to season, year to year, etc. The basic premise of Macdonald’s idea is that a fox (or pair of foxes) establishes a territory large enough to supply it with sufficient food during the hard times, when food is scarce. Logically, it follows that this area will most likely provide more food than the dominant pair need during the ‘good times’. This ‘surplus’ food could support additional foxes and, provided having these extra bodies on the territory doesn’t cost the ‘owners’ anything (i.e. they don’t go hungry), blood relatives may be permitted to live on the territory. When food gets scarce again, and the ‘hangers on’ start imposing a cost on the dominant pair, they’re forced out. This concept is known as the Resource Dispersion Hypothesis (RDH) and seems to explain group living in foxes (and many other carnivorans) nicely.

There are some cases where the basic premise of the RDH requires a slight modification in order to explain an observed situation and a good example of this comes from the group-living foxes of Bristol city. Prof. Stephen Harris and his colleagues at Bristol University’s Mammal Research Unit (MRU) have found that group living in these foxes is only partially consistent with the RDH or, more specifically, an additional concept needs including. Harris and his co-workers found that, in some cases, territory owners defended areas larger than was necessary even if they were planning for the hard times; i.e. even in bad times, the territory would still provide more than sufficient food for the pair. In two instances a territory was split, with the parents effectively giving half to their daughter. The suggestion is that foxes may opt to defend territories which are larger than absolutely necessary, provided the costs of maintaining larger areas (energy lost patrolling it, injuries sustained fighting with intruders, etc.) are not too high. This would provide the foxes with additional food security and would mean a given territory could support more than just the dominant pair more often than just during periods of abundant food – indeed, in all but the absolute worst times. Harris and his colleagues call this the non-minimal territory theory (NMT). In the end, it is the availability of resources within the territory (be they ephemeral or constant) that dictates whether additional foxes are tolerated. It may not, however, be the whole reason, particularly when it comes to explaining why vixens are generally tolerated but other dogs are not.

Fox cub following adult
Red foxes are solitary hunters and, even where they live in social groups, they invariably hunt alone. That said, as they get older cubs will often follow an adult out as they learn what to eat and where to find it. Cubs that are almost fully grown seen with their parents can often give the impression of a pack of foxes on a hunt.

I have mentioned that social groups are almost invariably composed of blood relatives (brothers, sisters, cousins, etc.) and in the vast majority of cases these are females: a group typically comprises a single dominant dog fox and dominant vixen along with several (four or five is not uncommon, and ten is the largest number of adults found in a single group in Bristol) subordinate vixens from previous litters. During the course of his studies in Oxford, Macdonald found that only very occasionally did more than a single dog co-habit and he never found any evidence of vixens successfully emigrating into an existing group (suggesting a familial relationship within the group). In Bristol, Harris and his team found that, although multiple dogs in a group was unusual, it was more common when the fox population was large; at high densities, they found subordinate males to be as common as subordinate females in social groups. The MRU biologists also found that older females that had previously been dominant sometimes remained within the group as non-breeding subordinates. In his contribution to the 1980 Biogeographica volume on Red fox ecology, Freek Niewold noted that vixens were tolerated to a much greater extent than dogs. Niewold described how:

A remarkable situation was created by closely related females (mother and daughter) who were occupying adjacent territories. Although the males were clearly separated, the females could freely visit each other after the division of their former common territory.”

While there are many examples of related females living together, or nearby, without any apparent animosity, there are also examples of dominant vixens violently expelling their daughters from the territory, particularly when she is raising cubs. Thus it seems that females are very flexible in their tolerance of one another. By contrast, however, it seems that aggression between males is endemic and various observations suggest that as the male cubs reach sexual maturity they are generally chased out of the group by the dominant dog, who presumably sees them as reproductive competition. This probably also serves to prevent inbreeding within the group (mating with close relatives), which ultimately improves the genetic viability of the population. Indeed, recent work by Eli Geffen at Tel Aviv University and colleagues suggests that, among canids, pack members are typically excluded as mates, although individuals may pair indiscriminately (i.e. irrespective of relatedness) outside of their natal group regardless of kin encounter rate. In other words, if the other animal is a member of their group, mating is automatically prohibited, while any animal is a potential mate (regardless of whether they're related) when encountered outside the social group.

While the RDH and NMT hypotheses provide a good basis for explaining why offspring may be tolerated in a typically solitary species, it doesn’t tell us why the foxes want to stay. This is an even more interesting question given that we know subordinate vixens rarely breed (even if they do mate they rarely give birth – see Breeding Biology) as their breeding is suppressed -- both behaviourally (by physical attacks) and hormonally (through the production of stress hormones) -- by the dominant vixen in the group. Initially it may seem that the best option for a sexually mature fox would be to leave the family group and set off in search of a territory in which to raise their own family; this is, after all, what genes drive their hosts to do – leave the family fold and spread copies into subsequent generations (this is called dispersal). Given that most foxes living in urban areas will only live through a handful of breeding seasons, it would seem that the clock is ticking to get their genes out there.  It seems that a crucial factor in determining dispersal is the local fox density. If the area is ‘saturated’ with foxes (i.e. the population density is high and there are very few, if any, available territories) foxes have to travel further afield looking for a territory of their own. This travelling uses a lot of energy and presents many challenges, including the risk of injury or death when fighting with another fox for a piece of land. Indeed, a study led by MRU biologist Carl Soulsbury, published in Behavioural Ecology and Sociobiology during 2008, found that dispersing foxes received more serious bite wounds than non-dispersing animals. Soulsbury and his colleagues also observed that while vixens were more likely to become dominant if they left home, males were no more likely to attain dominance if they dispersed than if they stayed on the natal territory. In some cases offspring may inherit the territory from their parents, or forcibly push them out, but this is by no means guaranteed and thus cannot be relied upon as a breeding strategy. It may sound from all of this like foxes sit there and weigh up the pros and cons of leaving home compared to staying at home but of course, they don't; these are just the biological processes driving what is innate behaviour. Instead, they stick around (because they generally enjoy the company of their family members) until they get that 'urge' to move on (often driven by the desire to breed) or are kicked out by their parents.

So, a fox may choose to remain on the natal territory to reduce the costs (dangers) associated with striking out on its own, and this is particularly likely when the local fox density is high and space at a premium. Indeed, tracking studies suggest that a fox will make several exploratory trips away from the territory before dispersing, during which it is presumably checking the local fox density (see Q/A). Choosing to stay at home, rather than dispersing, is known as philopatry. This is not, however, the complete picture and there are other benefits that both the philopatric fox and dominant pair may gain. To the dominant pair, having your offspring hanging around might offer support defending the territory, although the present evidence suggest that subordinates don’t engage much in this behaviour. Alternatively, if the kids are going to stick around, they could help with the chores – more specifically, they could help ‘babysit’ any subsequent litters. To the philopatric individual, staying at home may extend their life expectancy, and there’s the potential to learn from your parents or at the very least be in better condition come dispersal time. Before we look at the possible benefits of philopatry, however, we must address a question: If the fox’s genes are driving their spread into future generations, how can we reconcile an individual foregoing breeding?

Red fox cubIn evolutionary biology, there is a concept -- originally proposed by Charles Darwin in his The Origin of Species and later popularised by the eminent ecologist William D. Hamilton -- called Kin Selection. Kin selection is quite a complicated topic and I don’t want to go into much detail on it here – readers interested in learning more are directed to Chapter Six of Richard Dawkins’ 1989 book The Selfish Gene for an authoritative and easy-to-read treatment of the subject. Essentially, however, kin selection suggests that individuals have a vested interest in the survival of not only their own offspring but also those of their close relatives (brothers, sisters, nieces, nephews, etc.), because they share common genes. The result is that, by caring for your brothers and sisters you are helping to ensure that at least some of your common genes make it into subsequent generations. Thus, a philopatric vixen pays the cost of not being able to breed but in return she can potentially gain the experience of helping to raise her brothers and sisters in subsequent litters (which may put her in better stead if she has her own cubs one day) and, at the same time, by helping to ensure her relatives survive, she is helping to ensure that some of the family genes -- many of which she is also carrying -- survive. To those unfamiliar with evolutionary theory this may seem a little far fetched and they perhaps imagine foxes doing calculations to work out the genetic relationship of a particular cub to themselves before deciding whether to feed it! Foxes do not, of course, know anything about this process; it all happens subconsciously, having been programmed by the animal’s genes before birth. The process of kin selection is realised in foxes through emotions that we refer to as love or affection, not mathematics. It does, nonetheless, have the same effect. (Back to Menu)

In some cases philopatric animals (particularly females) will assist with the raising of subsequent litters of cubs: this is known as alloparental behaviour (raising, or helping to raise, offspring that are not your own). This assistance comes in the form of providing food for the cubs, grooming them and playing with them – in some cases these non-breeding vixens will defend them from intruders and, occasionally, they may even lactate and suckle the cubs. There are even reports of subordinates bringing up the cubs in the event of the dominant vixen’s death. Indeed, in his book, Running with the Fox, Macdonald recounts gamekeeper lore telling how, after killing a ‘milky’ vixen, it is not unusual to then shoot a ‘dry’ (non-breeding) vixen bringing food to the cubs and that some keepers have reported barren vixens attempting to dig out earths that have been gassed. Macdonald also witnessed group members bringing food to an injured adult family member that could not provision for herself. Where two dog foxes lived in the same family group, Macdonald observed both bringing food to the dominant dog’s cubs and, in Bristol, Harris and his colleagues found male and female helpers shared equally in duties.

Despite the above, some observers have failed to find any evidence that helpers actually help. In his book Foxwatching: In the Shadow of the Fox, for example, Martin Hemmington described an incident where a vixen he was regularly observing was confined to the earth with newborn cubs. Unfortunately, her mate -- who had up until now been providing food for her -- was killed by a car and the vixen was forced to go out looking for food (leaving the cubs alone). Hemmington noted that at no time did any of the other six subordinates in the group step in to take over the food provision, leading him to conjecture that perhaps these "aunties" only help with food gathering once the cubs have emerged. Indeed, this ties in with Macdonald’s observations of his fox groups in Oxford. He found that, although the dominant vixen was more amicable towards subordinates while she was pregnant (sleeping with and grooming them), this changed once the cubs were born; then the breeding vixen launched numerous ferocious attacks on them until the cubs were several weeks old, at which point the subordinates were permitted to babysit.

While subordinates do, in most cases, help the dominant pair raise the cubs, there is debate around whether this actually increases cub survival.  In a 1979 paper to the journal Nature, Macdonald described the case of a dominant vixen who sustained a serious injury to a front paw, leaving her unable to tend to her four week old cubs; during this period the cubs were found with the subordinate vixens in the group, with whose care they all survived. This certainly suggests that, in times of crisis at least, subordinates can step in and improve or even ensure the survival of the cubs. The situation that Torbjörn von Schantz found at his study site in Revinge, south Sweden, however, was quite different. In a paper to the journal Oikos during 1984, von Schantz described how cub survival in the area was actually higher in years when there were very few subordinates in the groups. Harris is of a similar opinion and data from Bristol suggest that helpers do not significantly increase the survival of the cubs. This is not unexpected, given that most cub mortality happens through factors other than lack of sufficient parental care which neither the parents nor the helpers can do much about (i.e. the cubs get shot, taken by predators, run over, etc.). Thus, as von Schantz concluded, it seems that helping to raise the cubs is a consequence of group living, rather than a cause of it.

The question of whether being philopatric provides valuable cub-rearing experience is also a matter of conjecture. Macdonald’s studies suggest that there’s more to being a good mother than practice and, in his 1987 book, he recounts how two vixens (neither dominant to the other) in one social study group became pregnant; one was pregnant for the first time (monoparous) having helped rear the group’s cubs last year, while the other vixen had successfully raised a litter the year before (multiparous). The monoparous vixen was an exemplary mother, but the multiparous vixen “became what can best be described as a nervous wreck, seemingly forgetting her diligent and successful qualities as a mother the previous year” and becoming very submissive to the monoparous vixen. When the last of the multiparous vixen’s cubs died, she became calm again and was apparently a diligent wet nurse to the monoparous vixen’s cubs. To the best of my knowledge, there are no statistics comparing the maternal proficiency of vixens who were helpers to those that weren’t, but Macdonald’s observations suggest that the previous successful rearing of cubs does not necessarily imply subsequent litters will be equally well cared for. Veteran fox friend Mike Towler points out that foxes are like people -- with each being of different character and intelligence, competence and capability -- and that this probably accounts for the variation in their parenting skills. Whether or not subordinates gain maternal or paternal skills from helping raise their brothers and sisters, Macdonald did observe that feeding cubs gave helpers increased confidence during encounters with the dog fox.

One final, and intriguing, account of a helper comes from the late New Forest naturalist Eric Ashby. In his excellent 2000 book, My Life with Foxes, Ashby described observing a wild fox bringing food to one of his captive cubs. Ashby recalled:

Once after dark, I noticed Sheba pawing noisily at her wire fence. As I approached, a wild fox ran away and there, partly pushed through the weldmesh, was a dead bat.

So, Ashby witnessed a wild (and presumably un-related) fox providing food for one of his captive cubs. Ashby's observations are not unique and Mike Towler is of the very distinct impression that any adult fox, regardless of gender, will look after a cub, regardless of the relationship. In his 2006 booklet, Just About Me, Towler described how his tame fox Cropper took care of three totally unrelated youngsters and, in a recent e-mail, he explained:

"I have witnessed adult vixens, including one collecting food for her own offspring, give precedence to released orphans who took food from, literally, under the noses of the adults. Always, the attitude was, "you're a youngster, you can have it.""

Such behaviour is not uncommon in Nature and it is not uncommon to find examples of adult animals (particularly birds) feeding unrelated youngsters - presumably the appearance and behaviour of young animals that causes their own parents to feed and care for them, can be rather more generically applied. Interestingly, however, this relationship doesn't last forever and, in foxes, it seems to breakdown during late June. Indeed, in a recent article to BBC Wildlife Magazine, Stephen Harris described how, come July, the adults visiting his garden no longer willingly hand over their food to the cubs, and may even steal food from them! Presumably, by this age, there is something about the way the cub looks or behaves that causes the adult to take the opinion that the cub should be starting to fend for itself.  I don't know what this trigger (or triggers) is, but it seems all animals understand that youngsters up to a certain age are still learning and are given more leeway than older animals. We see this in our own species (we know when a child is 'old enough to know better') and others - from domestic dogs to big cats and chimps, the adults of these species all grant that 'puppy licence' to youngsters. When the youngster reaches a certain age, however, such rambunctious behaviour is less welcome and often not tolerated. That said, even considering this puppy licence, Towler has observed that adult foxes expect cubs to show a degree of respect for their elders and adults will discipline young cubs if they push their luck too far. (Back to Menu)

Red fox with rabbit
Where subordinates remain in a social group they are invariably offspring from a previous litter and they may assist raising the current litter; they may bring food to the cubs, play with them, guard them, subordinate vixens may even suckle the dominant vixen's cubs.

Keeping order and knowing your place: the social hierarchy
Traditionally, canid social structure had been seen as a strict hierarchy with a ‘top dog’ (called an “alpha”) a second in command (a “beta”), possibly other ‘rungs’ (delta, gamma, etc.) down to the lowest member in the hierarchy (the “omega”), who bears the brunt of the others’ aggression. This is perhaps most familiar to those of us who own dogs and have, based on studies of wolf packs, been told we have to show our pet pooch who's boss. The hierarchical model, however, was established based on observations of unrelated captive animals who, with nowhere to go (there being no chance of dispersal in captivity), were forced to fight in order to establish a place for themselves in the ‘pecking order’ (so-called because it was first documented in chickens). Even David Mech, who conducted much of this early work, has warned against applying the model to wild populations. Indeed, recent work on domestic dogs has shown that these canids aren't stupid; they don't think humans are part of their 'pack' and, while it is possible for a human to enforce obedience through punishment, it is also possible (in fact, long-term, far more stable and rewarding) to establish the same level or obedience with positive reinforcement training. In reality, most canid social groups are nuclear families, consisting of breeding pair and several offspring from previous years. There typically is a social structure within the group, but it seems to be more flexible than the early studies suggested. Despite being familial fox groups still show a distinct social hierarchy, with some individuals being openly submissive to others. The heirarchy may not be fixed but an individual’s placement within it can determine their access to food; this can influence how quickly a cub grows, how much social contact an animal gets and how likely it is to disperse.

The hierarchy among the cubs develops early on and is modified throughout its life. Observations of captive foxes suggest that the foundations of a pecking order are evident in animals as young as one week old; the cubs pushing each other out of the way for access to milk. David Macdonald has observed that the individual characters of the cubs are discernable as soon as their eyes open (around two weeks old); the runt (or omega), who is constantly harassed and attacked by its littermates, is also evident from this age. It seems that, from about three weeks old, the cubs squabble over pieces of meat and the largest cub -- irrespective of sex, but typically a male -- is usually the alpha. Indeed, it seems that most animosity exists only when food is around, with cubs fighting fiercely to keep it by slamming aggressively into each other with sideways ‘body slams’. It is not unknown for fox cubs to kill (and eat) each other during this initial period of social establishment and it is estimated that about 20% of cubs die underground, many as a result of fights with littermates. In his article on how to watch foxes, published in the BBC Wildlife Magazine during 2007, Stephen Harris noted that the social structure among the cubs has been established around the time the cubs emerge from the earth (at about six or seven weeks old) and serious fights are rare from this point. While above ground, the cubs will spend much of their time play fighting, which helps not only to reaffirm their place in the hierarchy, but also develops their hunting skills and muscle tone, which will be crucial in later life. At the same time, foxes will groom each other, which helps reinforce social bonds and appears to provide pleasure to both parties. It has been suggested that a lack of grooming may induce social isolation and make an individual more likely to disperse come the autumn (see Q/A).

So, how does a fox group establish and maintain this hierarchy? Many readers will be familiar with the sights (perhaps more likely, the sounds) of fox fights but, while fighting does play a role in establishing and maintaining a hierarchy, it is not always required and if it is, it usually comes into play late in the encounter. Generally speaking, foxes don’t want to fight with each other – it uses a lot of energy and risks serious physical injury, even death. Consequently, foxes (indeed, canids in general) have evolved a suite of highly ritualised displays and vocalisations that help establish dominance. These displays take the form of exaggerated body posturing and facial expressions; much can also be conveyed by the position of the ear and tail and the state of the fur.

It is something of a generalisation, but a fox standing tall with an erect (or steeply upward sloping) tail, raised/bristling whiskers, and erect ears is dominant in an encounter – if the ears are flattened to the side of the head, against the neck, and the hackles on the back of the shoulders raised the animal is ready to attack. By contrast, lying on the ground with the head lowered, ears flat against the top of the head, tail curled underneath (or tightly alongside) the body and mouth agape is the typical submissive behaviour exhibited by foxes. Essentially, the dominant fox will walk tall, while the submissive animal will attempt to get as low to the ground as it possibly can; in the case of the vixen, the fox may even roll over, exposing the vulnerable stomach and genitals as a sign of submission. One cannot, however, base our interpretation of an encounter based soley on the body posture: the facial expressions of the foxes involved in the conflict are also highly significant. American canid biologist and veterinarian Michael Fox is responsible for much of our understanding of how dominance-submissive behaviour operates among the canids. Fox’s studies during the 1970s established that the ‘submissive crouch’ involved the animal remaining low to the ground, with its head extended, ears flat and eyes narrowed, with the gaze directed away from the dominant animal. A dominant animal, according to Fox's studies, stares directly at the submissive animal. Both animals may gape; their mouths may be open between 10-degrees and 60-degrees. It should be noted, however, that gaping and closed eyes does not necessarily indicate an aggressive encounter (see below).

In many cases, the two foxes are members of the same social group and the submissive behaviour of one to the other is sufficient to establish dominance. There are, however, cases where there is competition for territory or mates and one fox may be attempting to overthrow the existing territory holder – in such cases both will initially display dominant body language and a stand-off may ensue. The two foxes stand side-by-side, their backs arched, tails curled to the side, ears flat and their heads away from each other – often both will gape. This close proximity allows each animal to assess its opponent and, in some cases, one may immediately exhibit submissive body language and crawl angled away. Assuming that neither individual backs down, they will turn their heads to face each other and ‘body shove’ each other, testing their strength; this rapidly escalates into a fight, with each animal biting at the back of the neck and shaking. Each fox also attempts to bite the head (sometimes the rump) of the other; facial/neck injuries are common wounds found on foxes during the breeding season (when males are competing for access to females).

Fox trot
The ‘foxtrot’. Two foxes rear up on their hind legs and attempt to push each other back; the one that drops first is the ‘loser’. This encounter (between two almost fully grown cubs) has more to do with play than aggression, but the same method is used by adult foxes (particularly vixens) to fend off intruders or establish dominance.

In some cases, particularly when the combatant animals are vixens, the foxes may rear up to face one another, with ears flat, mouth agape, hind feet widely-spaced, tails curved out and downwards, with front paws on the shoulders of the other fox (holding each other at a roughly 45-degree angle): this is the aptly-named foxtrot (above). Unlike the elegant ballroom dance (which apparently gets its name from the actor Henry Fox who is credited with its invention in 1914), there is nothing smooth or sophisticated about two foxes engaged in a foxtrot – each attempts to push the other backwards, screaming with sharp explosive vocalisations (called ‘gekkering’) as they go. The ‘winner’ appears to be the one that successfully topples their opponent or causes their opponent to turn away. In some instances the ‘battle’ may be prolonged and end with both animals lying on the ground screaming at each other. Rarely, however, does a foxtrot end in bloodshed. Indeed, that is the point of this highly ritualised displaying – it allows the animals to establish dominance passively, without the need for violent combat (and hence serious injury). Despite how aggressive an encounter may look or sound, serious injury is comparatively rare. Cubs may sometimes foxtrot to settle disputes.

Many studies on fox society suggest that it is the dominant pair that is primarily responsible for territory maintenance and the dog appears to do most of the scent marking and fighting with interlopers. Fights among vixens are not, however, uncommon and a dominant vixen may squabble with other subordinate vixens in her social group, or engage in fights with neighbouring vixens. In some cases, the dominant vixen and dog may work together to see off an intruder. Macdonald recounted just such an encounter in Running with the Fox. He described a fight between two adult vixens that was accompanied by much gekkering and screaming as the two sideways barged each other, “parried fang with fang” and rolled together in what he portrayed as a ball of fur and teeth. The resident dog fox, alerted by the commotion from several hundred metres away, came flying across the field and collided with the combatants, knocking the interloping vixen off her feet; the dog proceeded to chase the interloper out of the territory into a hedge where the fighting continued until the dog emerged, a little further down, victorious. This dog fox walked out of the hedge with a stiff-legged gait (almost prancing) holding his tail “poker-stiff and slightly above the horizontal”; classic body language of a winning fox.

Macdonald’s account is an interesting one because vixens typically appear subordinate to dogs; a vixen generally greets a dog with her ears flat, squirming on the ground at the dog’s feet as she licks at his muzzle; she may also thrash her tail (see David Macdonald's photo below, right). The dog greets the vixen with his head held low, uttering a low ‘warbling’ sound. Hence, aggression is almost invariably intrasexual (i.e. males vs. male, females vs. females), rather than intersexual (i.e. males vs. females). Indeed, Macdonald goes on to describe a ‘fight’ between a dog and vixen from different territories at the boundary between the two groups in Israel’s Judean Desert. In this case the dog pirouetted on his hind legs, holding his paws close to his chest and stepping in circles around the vixen who was squirming on the ground in typically submissive style. The dog never followed through with his attack and the vixen never retaliated. Macdonald considered that the fact her adversary was male prevented the vixen from defending herself, while the dog was inhibited from attacking his opponent because she was female. Despite the occasional attack by a dog on a vixen, Macdonald never observed a vixen attack a dog and recent footage on the BBC’s AutumnWatch series of the foxes living on the Pitsea landfill site in Essex showed a new dog fox arriving on the territory who, despite being aggressive to the male cub from that year’s litter and being large, behaved submissively towards the dominant vixen.

Vixen submitting to dog foxIn fox society, the dominant pair tends to share the same hierarchical status (the dog is often dominant over the vixen, although there may come a point where the vixen has been as tolerant as she can and rebels!) and the fortunes of a subordinate can change depending on the presence of other group members. Related vixens may start out being friendly towards each other (sleeping, playing and feeding together) and, while this may continue for a long period, it can degenerate quickly with one becoming dominant over the other. When two vixens meet there are often (sometimes subtle) behavioural indications that one is dominant to the other; at the extreme a subordinate will greet a dominant vixen in the same way a vixen greets a dog, much frantic tail thrashing. Macdonald found that, in two of his captive vixen sisters, one was completely dominant over the other and rebuked the other if she was caught taking food or getting too close to the dog fox, with which she was apparently besotted. When the dominant vixen was removed, the subordinate returned to her previously calm demeanour; it seems that a few hours respite from social oppression is sufficient to restore behaviour, suggesting the traits of social status are only skin deep. When the dominant vixen was reintroduced to the group, the subordinate’s confidence collapsed again. In another example, Macdonald observed that a low-ranking subordinate rose instantly to the top of the pecking order when a new dog was introduced to the group following the death of the old one. Perhaps most intriguing of all is that a vixen’s status in one group may affect her treatment by members of neighbouring groups. Macdonald found that, in his Israeli study group, the dominant vixen in one group also appeared dominant to low subordinates in a neighbouring group, while she was subordinate to the two top vixens in the group. Presumably there is something in the demeanour of a fox that others recognise and use to decide whether they should be challenged, although the MRU biologists observed that dominant vixens frequently mated with subordinate males from neighbouring groups (but never subordinates within their own group), suggesting that they found it difficult to assess the status of their suitor outside of the group context. Perhaps it is easier to identify a subordinate vixen than a subordinate dog away from their group?

The above elucidates how fox society and hierarchies aren’t always as straightforward or simple to pigeonhole as we might hope. Some foxes are strictly territorial and will attack another individual as soon as they step across the boundary into their range. Other foxes only fight when an intruder breaches their core area or is spotted stealing food. In fox society coalitions may be formed to expel an intruding fox and there are even apparent reprisal attacks for the crime of stealing food. Indeed, food is pivotal in fox society and the cause of many altercations; from their first weeks of life cubs will fight ferociously to gain and keep hold of a meal. As Macdonald puts it:

If there is one thing in fox society that is ‘not done’ it is to approach somebody who is eating … foxes generally do everything possible to avoid even being seen with food and, if the worst comes to the worst, will at least turn their backs to each other while eating.”

Perhaps just as importance as knowing what the 'rule of engagement' are in fox society, is knowing how to make up for having broken them. Quite recently, Mike Towler described to me how he has observed foxes apologising to each other (and him) for having broken these rules. Towler explains:

"They have a system of apologising. Facing the other party, the fox lies down on its stomach in a straight line, forelegs like a pair of tramlines with the chin resting on them, and whimpers -- which I suspect to be a language. It is humility personified. I had witnessed it between foxes, then I was subject to it. Why? The fox had failed to recognise me, and fled. I called after her and when I caught up with her received this abject apology. Apology accepted, we went for a stroll together."

As autumn progresses, family cohesion begins to degrade and tensions rise, leading to more altercations within the group. It is often during this time that cubs will begin to leave in search of new territory and, from September onwards, the male cubs begin to mature sexually, increasing competition with their father, who will become increasingly intolerant of them. In some cases, subordinates may launch a coup and oust the dominant animal(s), although this appears rare. There is also some suggestion that, if the dominant vixen becomes barren (through old age), she may fall in the ranks and become subordinate to one of her daughters. Finally, some authors have observed two hierarchical restructures in a year. During his study on foxes in Alaska, Cornell University biologist Robert Vincent recorded a reshuffle in November just before the breeding season, which was often violent, and a second during February, during which less fighting occurred. Vincent noted that much of the hierarchy remained the same, except for the addition of dominant animals and the departure of the lowest members. The place an individual holds in the hierarchy following any reshuffling is important because it affects their breeding performance: as we have seen (see Breeding Biology), it is typically only the dominant animals in the group that breed. (Back to Menu)

Foxes play fightingAll in the name of fun: fox body language
Interpreting the meaning behind canid body language, and subsequently categorizing it, is not a straightforward task because there is a striking, albeit superficial, similarity between domination and play. Indeed, anyone who has witnessed domestic dogs playing together will probably have noticed that the ‘rough and tumble’ can appear quite aggressive to the casual human observer. While screaming and actions aimed at causing physical injury (i.e. biting, scratching, etc.) are good indicators that the animals are fighting, much body language (gaping, pouncing, erect ears and tail, rolling around together, etc.) appear in playful and aggressive encounters. Moreover, tensions can rise and fall quickly, such that what starts out as a playful encounter could end up an aggressive one. Macdonald found that, in his captive group, the dog often found it difficult to solicit play from the vixens because of their subordinate behaviour towards him; in one example, this led to the dog trying to drag the vixen to her feet, which involved grabbing her by the neck and trying to lift her off the ground. Macdonald conceded that to many the result could look murderous, with the vixen being dragged back and forth by the throat. Towler, by contrast, described no such issues in his foxes.

Beckoff noted there were usually subtle differences in some of the facial expressions when used for play rather than aggression. The play face, for example, involves opening the mouth by two-to-five-degrees and pulling the lips back horizontally; this is often accompanied by a brief shake of the head, before the animal darts off in a ‘catch me if you can’ pattern. In my experience, even full gapes can be associated with play and foxes may even bite at each other, although without any obvious ferocity. There is a calmer -- more ‘light-hearted’, if you like -- ambiance to the proceedings; when the foxes turn aggressive, the fur literally starts flying. One indication that the aim is play, rather than aggression, is to look at the tail. In How to Spot a Fox, Henry notes that a tail forming an ‘upside down U-shape’, combined with ears flattened to the side of the head signifies play.  In my experience, play bows are often employed, especially when foxes are trying to solicit play from domestic dogs or cats. Towler has many fascinating stories to tell about how foxes solicit play from one another -- I (and I suspect he) am hopeful that these will soon make it into a book he is looking to publish -- including how they gently grip each other (and sometimes Towler) as a sign of friendship and a gape with closed eyes being an invitation to play. Towler described one such incident in a recent e-mail:

"The mouth agape stance is a greeting, an invitation to play. That play may well be play-fighting -- fast furious and terrifyingly realistic -- but nobody gets hurt. How can I be so sure? Because I've been close alongside, even invited to join in. I have a photo of the initial invitation [see below] where the invitee even has his eyes closed."

Interestingly, one facial expression that seems to be lacking in the Red fox’s repertoire is the snarl. Despite some suggestions to the contrary in the tabloids, most authors seem to agree that foxes do not snarl.  Photos of foxes mid-chew, or at the start or end of a yawn can often give the appearance of snarling, but the skin and musculature of the rostrum is not pulled back to the same extent as in other canids. Indeed, Macdonald pointed out that a snarling fox was something you only saw in erroneous taxidermy specimens; Henry concurred, noting:

Foxes don’t snarl. Wolves do. Dogs do. But not foxes. Snarling is a ‘close-in’ facial expression useful in highly social animals like wolves and dogs, but not for the solitary fox.” (Back to Menu)

Fox play gape
This photo shows one of Mike Towler's foxes soliciting play from the other. It is not difficult to imagine that some would look at the photo and see an aggressive encounter, but the closed eyes, tail curled horizontally but not tight against or under the body and ears pushed to the side indicate the motivation is friendly. Here's Mike's explanation of the photo, reproduced here with his permission:

"Jack [right] is inviting Cropper [left] to play-fight, Cropper is accepting the invitation. Note that Jack has his eyes closed. The battle that then ensued would be terrifyingly realistic but nobody got hurt other than by accident. Once, Cropper got stuck with his fangs accidentally hooked up on the mesh walls of the pen. Jack took no advantage of Cropper's predicament -- other than possibly taunting him with insults. I rescued Cropper and the romp continued. Cropper also had play-fights down in the meadow with his wild chum, Echo. I was invited to join in. I declined because I knew that the foxes would then amend the play to contend with my lumbering ineptitude, spoiling the fun for them."

Nightly interactions
Despite spending much of their day resting together, foxes conduct the majority of their nightly business alone. Group members do, however, meet frequently, if fleetingly during the night. Tracking foxes in Oxford, for example, the WildCRU team found that members of the same group were in contact (either calling or face-to-face meetings) for 18% of the time, while they were in contact with members of neighbouring groups for only 1% of the time. Indeed, it seems that members of neighbouring groups actively avoided each other at boundaries. Intragroup meetings (i.e. two members of the same group) were friendly, while intergroup meetings (those between members of different groups) tended to be aggressive.

In Bristol, Pirian White and Stephen Harris also observed that foxes met group members more frequently than neighbours and that intragroup meetings were generally amicable, while intergroup ones were aggressive. White and Harris also found that intergroup meetings were more common during the winter, which is presumably a reflection of this being the breeding season. On average two neighbouring foxes met about once every one-and-a-half days during the winter, compared to only once every four days-or-so in spring, summer or autumn. Within the social group, each fox met another member twice per night, on average; this was slightly higher during winter than in other seasons. Subsequent studies of Bristol's urban foxes have revealed that dominant and subordinate individuals interacted with each other more frequently than dominant individuals interacted with one another; subordinate individuals also interacted with other subordinates more frequently than dominant-dominant dyads. In addition, the MRU’s dataset show that, among intergroup meetings, males met females more often than they met other males, or vixens met other vixens. (Back to Menu)

Communication: something to shout about
Foxes communicate with a variety of scent, vocal and visual cues. As we have seen, changes in body language or facial expression that may appear subtle to us convey a wealth of information to other foxes about the individual's mood, and can be used to settle disputes without the need for direct conflict. Indeed, the colouration of the fox may even have evolved to help communicate these body language messages. Henry was of the opinion that the light buff colour of the inner ear and the black of its back could be used like a semaphore system – rather than using two flags and various arm positions, the fox uses ear positions (with each position having a unique colour code) to signify its intentions to another fox. In addition, he considered that the white tip to the brush could act as a very obvious ‘white handkerchief’ of surrender:

I think the white tag of the tail combined with tail lashing has evolved as an attention-getting display that is effective even under reduced visibility.

Classic dominance and submissive body language is apparent in foxes from a very early age and is often easy to see if you feed foxes and have more than one individual visiting at a time. In cases where several foxes are feeding on the same highly localised food source (such as that at many garden feeding stations), some are clearly dominant over others. Along with some of the body language described above go various vocalizations. Indeed, the body language only tells part of the story; the noise that the fox makes while exhibiting a posture can alter the message being conveyed, and vocalisations are crucially important in fox society.

In 1963, German ethologist Gunter Tembrock documented 28 different types of call with an audible range of 100 Hz to 5,000 Hz; these included different calls for greeting, submission, alarms, contact, etc. More recently, in a 1993 paper to the journal Bioacoustics, Nick Newton-Fisher and his colleagues provided an analysis of fox vocalisations, based on 585 recordings. Using these recordings, and their observations of fox vocal behaviour in the field, Newton-Fisher and his team were able to identify 20 different types of call, eight of which are used exclusively by cubs – the majority of the adult calls were barks/yell barks. Indeed, according to an article in the February 2004 issue of BBC Wildlife Magazine by Stephen Harris, foxes make more than 20 different call types and call throughout the year, although they are most vocal in the winter. The vocal repertoire changes and broadens as the fox matures. Generally speaking, newborn cubs produce a "whelping" noise, which develops into a more rhythmic "yelping" noise by about three weeks old; the whelping and yelping noises are used by the cub when it needs attention or if it becomes isolated. Similarly, a lonely cub will apparently produce a warbling noise. A vixen will issue a sharp ‘cough’ at the earth that will send the cubs scurrying for cover and will summon the cubs with a low ‘growl’ (variously described as a 'mew', 'churr' or 'purr' and often involving a vibration of the stomach). Interestingly, there appears to be much subtle information contained within this call and Mike Towler has described to me how he frequently saw one of his vixens utter a soft 'mew' to which only a single cub would respond (the other five ignoring her). Towler told me: "To me it always sounded the same, but as only one specific cub would respond she clearly called by name and my hearing failed to register the difference." Recent advances in our understanding of animal communication has found that it's not just humans that have names (or equivalents); dolphins, for example, have recently been shown to have click trains that signify a specific individual. The most commonly heard call is either the sharp ‘yapping’ bark (called a Staccato bark) that seems to be used by members of the group to maintain long-distance contact, or the ‘wow-wow-wow’ bark, which appears to be a declaration of territory ownership. It is apparently possible to both sex foxes and recognise individual animals based on these vocalisations, although this may be complicated because both sexes can make the various calls.

Foxes may call at any time of year, although they are most vocal during the breeding season (in my experience, particularly towards the end of winter). Outside of winter, however, Harris’ foxes were pretty quiet; in more than 400 hours of tracking, the Bristol foxes made only 77 calls, each lasting only a few seconds.

The subject of what calls foxes make and what they mean is covered in an associated Q/A, as is the topic of how foxes communicate with scent. (Back to Menu)

Bottle-feeding Red fox cubInteraction with Humans: There can be few animals that inspire the range of emotions that the fox can – from adoration to vehement hatred. A good example of the spread of feeling was apparent from the readers’ letters published in the July 2006 issue of BBC Wildlife Magazine. The spectrum of opinion was broad; from a gentleman from Buckinghamshire whose partner maintained a hatred for foxes after one entered their house and killed a pet gerbil in their daughter’s room as she slept, leaving scat on the landing, to the story of a lady from Hampshire who found emotional comfort in a visiting fox during a very bad period in her life. The reasons behind a person’s attitude to foxes can be as broad as the emotions themselves. Typically people that dislike foxes do so for one of two reasons: they have suffered some personal trauma from one (this may be losing a pet, having their garden dug up, a bin raided, etc.), or they dislike foxes by proxy. In my experience, upon questioning people as to the reason behind their dislike of foxes, the response is often something along the lines of: “well they kill for fun, don’t they?” or “they’re mangy bin-raiding vermin”. Probing further it often transpires that they have never experienced the so-called ‘blood lust’ and, in some cases, have never actually seen a wild fox. The aforementioned subjects have been covered in detail elsewhere on this site (see Q/A), so I will not regurgitate the information here. I mention this only in relation to how our opinions of foxes -- indeed, wildlife in general -- can be so heavily influenced by what we read in the press and hear on the grapevine.

Many people will live their life never seeing a fox, others will have fleeting glimpses or brief interactions, but most will still maintain an opinion of the species. For many species, whether a person chooses to like or dislike them is generally based around how much inconvenience said species causes – the less the trouble, the higher the probability the person will like (or at least have no negative feelings towards) the animal in question. The Red fox, as we have seen, is different – it is so deeply rooted in our history and culture that most people have an opinion of it. Unfortunately for the fox, a great deal of the literature does not portray it in a favourable light. (Back to Menu)

The fox in literature and film
Reference to the fox as a cunning trickster can be found in some of our oldest literature: that of the Ancient Greeks, the Romans and the Hebrews, although translators of The Bible’s Old Testament appear to have occasionally confused foxes with jackals. Foxes feature in 51 of 6th Century BC Greek writer Aesop’s 600-or-so fables and, although he appears to admire their intelligence, they are often portrayed conning another animal. In some fables, however, the fox is used as a surrogate for exploring human emotions, behaviour and lessons in morality. Aesop’s The Lion and the Fox fable, for example, highlights our fear of unfamiliar things and how this fear can be overcome with patience. Perhaps one of Aesop’s most famous fables, The Fox and the Grapes, tells of a fox lusting after grapes hanging from a vine just out of its reach; the fox tries desperately to reach the grapes but cannot and, in the end, he gives up saying that they weren’t ripe anyway and he didn’t want any sour grapes. This story illustrates a phenomenon that psychologists call “cognitive dissonance”, which essentially means that we reduce our disappointment in not being able to attain something by criticizing it, or telling ourselves/others that we didn’t want it anyway. Rumour has it that the common expression ‘sour grapes’ originates from this fable.

A common incarnation of the fox in early literature was Reynard. Reynard was originally called Reinardus, taking his name from a Latin poem about a wolf called Ysengrimus written around 1148 (possibly by the Flemmish priest Nivardus of Ghent). In the poem Reinardus torments his not-so-bright uncle Ysengrimus. It wasn’t until more than two decades later, in 1175, when Pierre St. Cloud published his poem Roman de Renard that the modern Reynard emerged as a central villain in the saga – the character spread across Europe and arrived in Britain sometime during 1250. Reynard’s profile was raised in Britain by his appearance in Geoffrey Chaucer’s 1390 Nun’s Priest’s Tale, where he appeared as ‘Rossel’. It was apparently from English writer William Claxton’s The Historie of Reynart the Foxe, published in 1481, that Reinardus became known as Reynard. The stories in which Reynard has appeared have been told and re-told, undergoing the usual modifications, but the central theme remains: that Reynard is a treacherous, vindictive, rebellious and ingenious loner, to be trusted at your peril. The character Reynard the Fox has appeared in various films, books, ballets, cartoons and TV advertisements. The reader is directed to WikiPedia’s page on Reynard for a more detailed history.

More generally, the fox appears frequently in popular culture, featuring in more than 70 movies (animated and live action), referenced in at least a dozen songs, three opera-ballets and countless books. There are also at least five web-comics featuring foxes, including the very popular Faux Pas comic strip by Margaret and Robert Carspecken, which began in 1979. Movies of particular note include the Belstone Fox released in 1973, Gone to Earth in 1950, Mark Rydell’s The Fox released in 1968, the fox taking the lead role in Disney’s Robin Hood and Colin Dann’s 1979 children’s story The Animals of Farthing Wood. Again, the reader is directed to WikiPedia’s page on Foxes in Popular Culture for a fairly comprehensive list. Before leaving this subject, a fox playing the role of the hero (as it does in Disney’s interpretation of Robin Hood and in Dann’s tale) is interesting because, particularly in children’s literature, such instances are comparatively rare. Indeed, from an early age children encounter animals that are given names and ascribed personalities according to the ecological niche they occupy: typically, predators are ‘bad’ and their prey is ‘good’. Consequently, the fox is usually tagged as the villain of the piece. As early as the 1870s, we encounter Br'er Fox (pronounced “briar fox”) -- the principal villain in American journalist Joel Chandler Harris’ book, The Uncle Remus Tales -- trying to trick (and being ‘out tricked’ by) Br’er Rabbit. Similarly, we encounter a ‘foxy-whiskered gentleman’ trying to trap the lead character in Beatrix Potter’s 1906 children’s classic The Tale of Jemima Puddle-Duck. Predators aren’t, of course, ‘evil’ any more than the animals they prey on are ‘good’. Animals do what they must to survive, without thought for the ‘feelings’ of their adversary. Nonetheless, even as adults, the portrayals of animals that saw us through our childhood can be difficult to shake, and this can cloud our judgement when it comes to interpreting the actions of the wild animals with which we share our planet. (Back to Menu)

Jemima Puddle-duck
A model scene from Beatrix Potter's 1906 children's story The Tale of Jemima Puddle-Duck, at The World of Beatrix Potter Attraction in the Lake District, showing Jemima and the fox that tries to eat her.

The emblematic fox
The fox is considered by many to represent the very essence of the wilderness, featuring in the legends of several Native American tribes. There is also a charming Eskimo legend telling how a fox outwits a raven, saving the tribe from starvation in doing so. Consequently, the fox features in much early artwork and features frequently as totem animals; bringing favour from the gods and helping the dead migrate to the next life. Even today the fox appears in our advertising and logos. The fox is, for example, the animal emblem of Leicestershire, featuring in the logo for the County Council (below). The fox also appears on the Arms of Leicestershire (the coat of arms for Leics), granted to the county in 1930 by the College of Heralds. The fox’s presence on the Council’s logo and the county crest infers the rich hunting tradition in Leicestershire – it is believed that organised fox hunting in Britain originated in the county at some point during the 1690s. The crest bears the motto “For’ard, For’ard” below the shield; For’ard is apparently a call used to encourage the hounds and drive them forward when hunting. The oft-cited ‘father of fox hunting’, Hugo Meynell, lived in Leics and was master of Quorn Hunt (one of the world’s oldest fox hunting packs, established in 1696) between 1753 and 1800 – he is credited with pioneering the characteristic high-speed open field chase seen in modern fox hunting.

Leicestershire County Council Logo FoxFoxes sometimes turn up as mascots for various sports teams, including the Leicester Country Cricket Club, Leicester Football Club, New Jersey Newts basketball team and Falkirk Football Club. They’re also used in various advertising campaigns -- including for Old Speckled Hen bitter brewed by the Moorland Brewery in Suffolk -- and, in the 1970s, car manufacturer Audi launched a car in the USA that was ‘swift and agile’ (compared to the other American cars of the time, at least) and aptly named the Fox. Audi produced 1.1 million of these cars (sold elsewhere in the world as the Audi 80 B1) between 1972 and 1978. Foxes also appear in place names and, according to Derek Yalden -- in his 1999 book The History of British Mammals -- in Scotland, the name madaiah ruaidh (‘red dog’ or fox) appears in at least six place names, while the Gaelic for fox (sionnach) crops up in a further 17. The fox is commonly used in the names of public houses, particularly in Britain, where a cursory search of an online pub directory reveals at least five pubs with fox in the name (including The Fox and Anchor, The Fox and Hound and The Fox and Pheasant) in London alone, while a more detailed search of the Yellow Pages found 315 pubs with fox in the name within the UK. (Back to Menu)

Foxes held in high esteem: gods, devils and worship








The fox as a resource: fur, meat and sport
For most of the history of fox interaction with humans, when it hasn’t been actively vilified or deified by religious cultures, it has at best been considered a pest to be exterminated. In some cultures, however, the fox has long been viewed as a commercial resource, with some evidence that as long ago as the Stone Age in Britain people were trading fox furs for goods (and possibly services). We also have records, dating from several Bronze Age sites, of humans using fox fur and at least one record of fox skinning from the Iron Age. There is evidence that the Romans wore fox fur (and even had foxes as trophies) and there is much evidence for the use of foxes for their fur during the Mediaeval period. In a paper to the journal Archaeofauna back in 2003, Ian Baxter and Sheila Hamilton-Dyer report on a large assemblage of animal bones from Saxo-Norman deposits (10th to 12th Century) in Hertford. Among these bones were the remains of several foxes and the archaeologists suggest that -- because most of the remains were foot and tail elements, which are typically left in furs -- these bones may represent evidence of the commercial exploitation of foxes by these settlers. According to an article in New Scientist by David Macdonald and Geoff Carr back in 1981, a full length fur coat includes about 14 fox pelts, while a short one has about eight.

The International Fur Trade Federation (IFTF), on their website, point out that the fur trade has a long and fascinating history, stretching as far back as the Stone Age, when fox skins were first worn by man.  Many ancient Mediterranean civilisations, including the Phoenicians, the Greeks and the Romans, seem to have attached great ceremonial importance to tanned animal hides, which were seen as a symbol of power and luxury.  According to the IFTF, in Northern Europe, fur began to be worn as a fashion item as well as for warmth from the 10th century. In his 2006 book, Fox, Martin Wallen describes the history of fox fur farming and, in his summary, he notes that prior to mid-18th Century, few people wore fur (it was still associated with Barbarian clothing) but from this period foxes began being hunted for their fur to be sold commercially and, by 1785 fox fur had found a place in Western fashion. Fur in fashion really took hold in the 19th Century and there was serious money to be made trapping foxes in America’s Pacific Northwest. Trapping foxes is, however, often difficult and tiresome work and, in 1890, Charles Dalton and Robert Oulton joined forces to start ‘ranching’ (i.e. farming) Arctic foxes commercially on Canada’s Prince Edwards Island (PEI). From PEI the practice spread and, by 1913, farms had become established throughout western Canada, into the USA and across into Eurasia. By the 1920s fur farming was the third largest business in Alaska (behind fishing and mining) and, by 1925, there were almost 400 fox farms -- holding some 36,000 foxes -- operating throughout the Alaskan Islands. Wallen notes that the Great Depression of the 1930s dealt fox farming a blow, causing trappers to eradicate many of the populations they established, although the business was still profitable when compared with other forms of agriculture.

Fur farming remains a substantial industry today, although it is currently illegal in the UK under the Fur Farming (Prohibition) Act 2000 and the Fur Farming (Prohibition) (Scotland) Act 2002. There is some small scale fur farming (mainly mink) in Republic of Ireland and elsewhere some countries have banned fur farming in certain states/provinces, while others (the Netherlands, for example) have banned farming certain species, including foxes, for their fur. According to the European Fur Breeders Association (EFBA), as of 2010, there were 7,200 fur farmers within the EU member states, with the main fur farming countries being Denmark, Finland, Norway, Sweden, The Netherlands and Poland. The farms produced fur worth an estimated 1.5 billion Euros (1.2 bn GBP or 1.9 bn USD) in 2010 and Finland is currently the largest producer of fox pelts in Europe, accounting for more than 81% of European production. Elsewhere, the IFTF estimate that the Canadian fur trade is worth 800 million CAD (about 500 million GBP or 600 million EUR), while the value of the US fur industry is estimated at 1.8 billion USD (1.2 bn GBP or 1.4 bn EUR). The IFTF estimate that 85% of global fur is supplied by farmed animals, while the remaining 15% is wild caught (i.e. trapped).

Fur farming is a highly controversial subject, not least because of the conditions in which some animals are kept. Generally it seems that foxes are kept in small cages in sheds and, once their fur has reached the required density, they are electrocuted and skinned. Much has been said about the poor state in which these foxes live. Indeed, a quick Internet search will bring up as many fur farmers extolling the quality of the living arrangements of their animals as animal welfare websites describing soiled battery conditions. One thing is for sure: much work has been done -- and still continues -- to establish how to improve the living environment (both in terms of the impact it has on the fox’s physical health and its ‘emotional’ well-being) for the animals and we have learnt much about fox behaviour and biology in the process. During 1980s the anti-fur movement became organised and their campaigns are considered partly responsible for a decline in the popularity of fur during the 1990s. However, Wallen, -- who appears generally anti-fur farming based on the tone of his book -- makes an interesting point that boycotts of fur by animal rights often overlook the impact this can have on indigenous communities, which are often heavily reliant upon the revenue generated from the trapping. It is certainly a complicated and contentious issue and I should point out that the foregoing does not mean that I endorse the farming of animals for their fur. I have read some truly horrific stories about animals being abused or skinned alive and, at the same time, seen some of the strides in the improvements in living conditions designed by researchers at the Norwegian University of Life Sciences. This website is not, however, a platform for me to air my views and as such I will leave the reader to draw his or her own conclusions based on the evidence they find.

Fox fur and skins
Fur farming is illegal in many parts of Europe and strictly controlled elsewhere. Illegal trapping of wild animals can be very profitable and authorities often confiscate furs and skins from trappers operating without a licence.

Generally speaking, mammalian carnivores don’t eat the meat of other mammalian carnivores and this is as true for humans as it is for wolves, bears or lions. There are several reasons for this, not least because carnivores tend to be more difficult and dangerous to catch than herbivores. Additionally, many carnivorans (particularly felines) derive much of their energy from protein, while also consuming a lot of fat (rather than the more balanced diets of many primates). The ammonia produced during protein metabolism can give carnivoran meat a pungent smell, while the high lipid content can make the meat greasy. There are also concerns about parasite (particularly hyatid worm) transfer via the meat, which makes the way the meat is handled and cooked very important. These factors combined tend to make foxes unpalatable to most humans. There are, as with everything, exceptions and some tribes (including the Kazakh people of Western Mongolia) eat fox meat, as do people in some developing countries, although perhaps more out of necessity than preference. Some private hunters also occasionally consume the meat of the foxes they shoot, although my research suggests that it’s generally not common. Based on what I have read on Internet forums, it seems that where fox meat is eaten, it is generally slow-cooked as part of a casserole and, even with such long cooking, the meat is often still tough. Nonetheless, in April 2011 JM Danslow butchers in Gravesend, Kent started selling fox rump meat. The meat is imported from farm-reared foxes in Denmark and Sweden and, according to an article in The Metro, the meat has a minty taste, not dissimilar to lamb.

Finally, the fox is perhaps the best known ‘animal of sport’ in the British countryside and, for many, hearing the word fox will conjure images of mounted hunts racing across the landscape. Fox hunting, and its history, is a complicated and long-running story about which many books have been written. I could not hope to cover the entire history of fox hunting in this article and as such I shall stick to the pertinent developments concerning fox hunting for sport in Britain. Readers interested in a more detailed account of this subject are directed to WikiPedia’s page on the subject. There is also a, now rather out-dated, review of fox hunting elsewhere on this site, while the question of how we control foxes is discussed at length in an associated Q/A.

As a small, highly adaptable opportunistic carnivore, the Red fox has always experienced the sharp end of man’s disdain. Indeed, in his fascinating 2007 book Silent Fields (an account of Britain’s general mistreatment of its wildlife), Roger Lovegrove describes the fox’s relationship with man as schizophrenic. Indeed, killing foxes was always seen as a form of pest control, with few people taking much interest in it; until, that is, foxes were identified as ‘beasts of chase’ and hunting parties were established. Precisely when the first fox hunt took place is lost in the annals of history. In Running with the Fox, David Macdonald notes that fox hunting has its origins in the Middle East during the 4th Century BC, or possibly earlier. In Britain some of the earliest records of foxhounds date back to the Romans during AD43. It seems that foxes have been hunted sporadically in Britain, typically by the monarchy, since at least Norman times (AD 1066), although it wasn’t until the late-1200s that Mediaeval laws on fox hunting became formalised, with Edward I widely reputed to have held the first royal pack of foxhounds. The oldest English book on hunting, The Master of Game, translated from a French text around 1420 regarded the fox as game, but of a lowly order; the fox was a Beast of Chase, rather than a Beast of Venery (i.e. hunting) like Red deer and Wild boar, which were under the king’s protection. The earliest fully documented fox hunt dates to Norfolk during 1543 but at this time game (i.e. deer) were regarded as the main quarry. It wasn’t until the Enclosure Acts started being passed in 1760 that fox hunting became more popular; these acts divided up the forests, making deer hunting more difficult. Indeed, even before this, it is widely considered that the destruction of deer parks during the Civil War in the mid-1600s led to the fox being substituted for deer as a quarry for hunts. Hunting with hounds as we know it today -- i.e. on horse-back over open country -- is widely credited as the creation of Leicestershire-based Hugo Meynell, master of one of Britain’s oldest packs (the Quorn Hunt, established in 1696) during the late 1700s. Fox hunting has had its ups and downs since this time, but has continued in roughly the same guise. At the time of writing (January 2012), the Masters of Foxhounds Association lists 334 active British hunts in its directory.

In England and Wales, as of 18th February 2005, the Hunting Act (2004) made it illegal to hunt various species of game (most notably foxes, but also deer and hare) with a pack of dogs. There are several concessions that the Act does permit to ensure that genuine pest control can still be carried out, including using up to two dogs to flush a fox to waiting guns (or, bizarrely, a bird of prey). The Act remains highly controversial and some have found apparent ‘loop holes’ in the law, largely because it is ambiguously worded. Indeed, I have seen some people interpret certain parts of the Act as meaning that if your dogs flush a fox while you’re out for a walk, you’re obliged to kill it. This is, of course, not the case. Schedule 1 section 7 of the Act, for example, states that:

Reasonable steps must be taken for the purpose of ensuring that as soon as possible after being found or flushed out the wild mammal is shot dead by a competent person.

The point is that if you’re out hunting foxes and plan to kill the foxes you encounter, you must shoot the fox as soon as is safe to do so once your dogs have flushed it – rather than letting your dogs chase the animal or letting the dogs kill the fox. If you happen to be out with your dogs for some reason other than hunting foxes and they flush one, you are not obliged to shoot it – just to call your dogs back. It has been argued that the Hunting Act has not, and will not, save the life of a single fox. This is likely to be true, but this is missing the point. The aim of the Hunting Act was not to afford foxes any form of conservation -- Red foxes are not endangered and show no signs of being in need of conservation in any part of their range -- it was to try and regulate the manner in which the fox is killed, to make it as humane as possible. Death down the barrel of a shotgun or rifle is generally considered a more humane method of dispatching a fox than is a pack of hounds. The debate over hunting with hounds is far from over and there is talk among the current Coalition Government of the UK to give the House of Commons a ‘free vote’ on the Hunting Act, which could potentially start a repeal process. Whatever happens, fox hunting always has been, and probably always will be, a controversial issue; the first opposition to the sport came from the Humanitarian League back in the late 1800s. (Back to Menu)

Red fox entering earthThe verminous fox: foxes as pests
In a world where humans keep animals as cherished pets and rely on them for a source of income, any animal that could potentially see these critters as prey or competition is unlikely to be welcomed. In Wild Mammals and the Land, a 1951 publication by the Ministry of Agriculture, the authors considered that:

War on the fox must continue to be the order of the day, and such warfare must be carried on by every means and with every weapon that is both practicable and humane.”

Indeed, for centuries foxes have been breaching the security of smallholdings and leaving damage in their wake. Consequently, many are of the opinion that the fox is a major agricultural pest and that the only good fox is a dead fox. I cannot even begin to estimate how many times I have heard someone say that foxes kill for ‘fun’ or ‘sport’, breaking into a chicken coop, slaughtering all the birds and taking only one (or in some cases, not taking any). I have discussed this subject many times on this website, indeed in this article, but few people who feel they’ve been aggrieved by the fox are willing to listen to the rationale behind their actions. In some ways, I can understand this: after all, knowing why it happens doesn’t bring back your chickens. Problematically, many people seem of the opinion that it is their right to keep chickens free range in their garden without fear of them being nabbed by a predator. A fox should know and respect the boundaries. Foxes are, however, opportunistic carnivorans; food is food to them and they don’t stop to think whether they’re going to annoy or offend any humans in the process.

I’m not aware of any recent surveys in the UK, but in the southern German city of Munich during 2000, Andreas König surveyed the attitudes of suburban residents’ to urban foxes and found that, while few of the respondents were scared of the fox, just over half thought numbers should be controlled to reduce the threat from the fox tapeworm, Echinococcus multilocularis (see Parasites and Diseases). More than half of the respondents were pleased to see the foxes about and considered that they had a right to live there. In Britain, a joint survey during the late 1990s by The Mammal Society and People’s Trust for Endangered Species found that foxes were the fourth most commonly recorded species in gardens, occurring in 68% of surveys. Despite such abundance, many (admittedly now dated) surveys suggest comparatively few complaints are made to local councils. A study published in 1985 by Stephen Harris at Bristol University looked at the number of complaints made to local councils about foxes – in an area of London with a population of just under 300,000 there were about 400 complaints per year. In Scotland, a survey published in 2007 revealed that only Edinburgh and Glasgow councils received more than 50 complaints per year; most urban areas received fewer than 25 complaints per year. While writing this article I attempted a vox pop of some local councils in order to try and find out how many complaints were made to them regarding foxes. The problem, it transpired, was that because councils typically don’t consider foxes as vermin any calls relating to them are forwarded to the appropriate body (The Fox Project, National Fox Welfare Society or, in the case of my local council, the RSPCA) and no records are kept. The pest control officer at my local council did, however, tell me that complaints about foxes have always been, and continue to be, very rare in Southampton city. Nonetheless, as David Macdonald pointed out in his fascinating article to BBC Wildlife Magazine in October 1985: “It is difficult to calibrate nuisance.” Indeed, what may seem a trivial disturbance to us may be a considerable inconvenience to someone else – all of this means that it is very difficult to accurately assess the pest ‘status’ of the fox in Britain.

Nonetheless, for centuries, the fox has been seen as a pest by man, who has gone to considerable lengths to reduce their numbers. Perversely, some authors consider that, were it not for mounted fox hunting the fox would have been eradicated in Britain. Indeed, as early as the late 16th Century, royal chronicler Raphael Holinshed wrote to Elizabeth I saying that, were foxes not ‘preserved for the pleasure of gentlemen’, they would’ve been eradicated many years ago. Robin Page, in his A Fox’s Tale, noted something similar:

In some rural areas foxes still have many enemies, but as long as people hunt they will ensure the preservation of their quarry. Consequently, rather than posing a threat, hunting offers the wild country fox its greatest insurance against excessive persecution.”

There is certainly much evidence to support claims that hunts played a significant role in maintaining or even boosting fox numbers in their parishes. Indeed, some authors consider that the start of live foxes being seen as a positive economic resource in Britain probably stems from the ‘bagmen’ who reportedly sold animals to hunts to boost/maintain numbers for their sport since at least the mid 18th Century, and throughout much of the 19th Century – some authors suggest it started during the 17th Century, or even earlier. In his book Town Fox, Country Fox, Brian Vezey-Fitzgerald described how foxes were imported from the European continent to Britain as numbers ran low from over-hunting and disease. Vezey-Fitzgerald suggests that, during the mid-1800s, foxes were being imported and released into the British countryside at a rate of more than one thousand per year. It seems that many of these foxes were arriving from Denmark and being traded through London’s Leadenhall Market, although animals also arrived from other countries (e.g. Austria, Germany, Italy, Sardinia, Scandinavia and even Russia) and were moved within the British Isles; notably from Scotland to England. Foxes arriving from Europe were shipped across onboard cattle ships in small cages and sold for the princely sum of 15 shillings (equivalent to about £40 today, according to The National Archives) and, according to Martin Wallen, in Fox, some regular customers had rolling orders for these animals. This trade in bagged foxes was controversial, even at the time, because the European foxes apparently often failed to give a good run. Fox bagging was, however, happening much closer to home, with some poachers digging out foxes and selling them back to the hunts on whose turf the foxes had been taken! Indeed, in his opus, The Red Fox, Huw Lloyd tells how hunts used to pay ‘protection money’ to poachers to guard against such raids on their earths as well as compensating farmers and gamekeepers for any loss of livestock on their beats.

So, hunts have invariably played a role in boosting Britain’s fox population over the centuries and it seems possible that, without the assistance from hunts, foxes may not be as widespread in the British Isles as they are today. I suspect, however, that it is optimistic to suggest that without hunts foxes would have been wiped out from Britain. That doesn’t, however, mean that considerable effort and resource hasn’t been directed at reducing fox numbers in Britain.

Mounted Fox HuntLloyd suggested that, in Britain, the first organised control of foxes (coupled with the hunting of foxes for their pelts) probably began with the appointment of the royal Fox Hunters of Edward I during the 13th Century. Subsequently, Tudor legislation passed by Henry VIII in 1532 introduced bounty payments for avian vermin control, part of a series of legislation (collectively known as the Tudor Vermin Acts) passed with the goal of protecting the grain crop following a series of poor harvests. The Act, entitled An Acte made and ordeyned to destroy Choughes, Crowes and Rokes (i.e. Jackdaws, Carrion crows and Rooks), set out bounty payments to encourage the killing of corvids. Henry’s Act was renamed in 1566 by his daughter Elizabeth I, who expanded the list of animals considered vermin. The 1566 Act, entitled An Acte for the preservation of Grayne, offered cash payment for proof (usually in the form of a head) of the destruction of one of a considerable number of bird and mammal species, even though many posed no obvious threat to grain supplies. Bird species on this ‘hit list’ included a diverse range from house sparrows and starlings (even kingfishers!), through the corvid species Henry disliked so, to harriers, kites and eagles. Among the mammals, bounties were offered for foxes, badgers, weasels, polecats, moles and even hedgehogs – the price paid for proof of a dead fox was one shilling, which -- according to The National Archives’ website -- was the equivalent of earning about £16 (19 EUR or 25 USD) today. Presumably, the inclusion of animals such as foxes was more for preservation of livestock than grain, given that they’re actually more beneficial than damaging to the harvest because they prey heavily on granivorous rodents! Regardless, these vermin payments continued until the early 19th Century (at which point gamekeepers were largely responsible for vermin control on estates) before the Act was repealed in 1863. For a detailed and authoritative exploration of the Tudor Vermin Acts, the reader is directed to Roger Lovegrove’s superb 2007 book Silent Fields.

It isn’t known how many people were involved with killing foxes under the 1566 Act, but Lovegrove’s examination of parish records suggests that there was massive variation in culling effort across Britain, with most effort being directed in the ‘ancient countryside’ of the southwest of England, the Marches, Kent and the uplands of Wales and northern Scotland. The Tudor Vermin Acts were aimed at a broad reduction (even eradication) of pest species, of which foxes were one, but some areas saw the formation of groups dedicated to the removal of foxes. Fox destruction societies were established, largely in areas where there were no mounted hunts (e.g. Wales and Northern England), during the Second World War. Lloyd notes that most societies were setup between 1941 and 1944, initially with funding from the government (I believe, although Lloyd doesn’t say, under the Assisted Fox Destruction Scheme); government support was withdrawn in August 1979. Approved societies offered a bounty payment of £1 per adult fox and 50p per cub (half the money coming from the government, pre-1979), although Lloyd mentions that in the latter years of the societies, as much as £2.50 could be paid for vixens. When Lloyd compiled his opus (during the mid-1970s) there were 221 societies operating in the UK, with 6,000-or-so bounties being claimed each year between 1968 and 1972 in Wales and 11,000 claimed in Northern Ireland during 1969. The Master of Hunts Association tells me that they don’t know of any destruction societies still in operation within the UK.

Currently, in the UK, it is the responsibility of local councils to decide which species are considered vermin. To the best of my knowledge, no council currently considers the fox vermin and, as such there is no requirement for them to take action to reduce fox numbers (as there is for, say, rats and mice). Indeed, there is no ‘official’ vermin list. My local council’s pest control officer told me that there is no formal information from DEFRA to say which species are considered vermin and must thus be controlled. Instead, the councils populate a list based on current legislation -- e.g. Pest Act of 1954, Prevention of Damage by Pests Act of 1949, etc. -- and the ADAS Pest Manual (now The British Pest Management Manual), published by the British Pest Control Association. The result is that there may be variation from council to council with regards to the pest species they control. My local council, and many around the country, do not (and have never) provided any fox control. That said, following a series of high profile incidents where foxes were alleged to have bitten people, in 2010 Sir George Young (Leader of the Commons) said that the government would consider whether the law should be changed to force councils to control urban foxes.

In his 2000 summary on fox biology and control in the countryside, Game and Wildlife Trust (GWT) biologist Jonathan Reynolds described how the persecution of foxes waned during the early 19th Century as the Industrial revolution saw the movement of people into towns and the development of wire netting to protect livestock. In addition, two World Wars resulted in many gamekeepers being called into active service, leaving an estimated 10% behind. Further disruption to the control of foxes came as the 20th Century progressed and many of the previously common methods of killing foxes were outlawed. Reynolds noted that many poisons were outlawed in 1911, while gin traps were banned in England in 1954 (although they remained legal in Scotland until 1973), self-locking snares became illegal in 1981 and gassing earths with cyanide effectively became illegal with the introduction of the Control of Pesticides Act (1986). In essence, farmers and gamekeepers can now use only free-running snares (the use of which is strictly regulated) or they can lamp at night with a suitable calibre weapon: the most effective and humane method of culling foxes is probably with a lamp (to pick out the eye-shine and body shape of the fox) and a heavy calibre rifle -- i.e. a .243 or .222 centre fire -- and the employment of a long-dog to recover any wounded animals. Shotguns could also be used, provided a sufficiently heavy load is used (i.e. not birdshot), but an air rifle would be unacceptable.

Early morning foxMany arguments have been had about the practice of shooting foxes and the potential for too many wounded animals to escape and die an unpleasant death (a debate raged between Bristol University biologists and a team at a Welsh wildlife consultancy in the journal Animal Welfare between 2005 and 2006). There are no statistics on how often, if ever, this happens although some studies suggest that ‘winged’ animals heal quickly and resume normal activities. Assuming, however, that the shooting is undertaken by a competent person, it is difficult to see how shooting is any less humane than the alternatives. The problem, however, is that shooting can be very labour intensive because the pressure needs to be maintained if the population is to remain suppressed. Foxes are, as a species, very resistant to culling because vacant territories (generated by the shooting of the resident animal) are rapidly filled by dispersing animals. The result is that fox control is a continuous activity, carried out throughout the year on many game estates (farmers may only deem it worth the effort and expense to cull foxes at particular times of the year – lambing time, for example). Moreover, in heavily managed populations, foxes can become very secretive, making it more difficult to find them in the first place. In addition, firearm restrictions make it highly impractical (arguably illegal) to shoot foxes in urban areas as part of any reasonable-scale control programme. There are exceptions, of course, and a home owner can pay a pest controller to shoot a fox visiting their garden, although such actions tend to have only short-lived results. Culling can be an option to remove particularly problematic animals (these crop up from time-to-time) but, more generally, as former Bristol University biologist Pirian White and his colleagues say in their 2000 paper to the Lord Burns’ Committee of Inquiry into Hunting with Dogs:

“… there is no clear relationship between fox abundance and levels of damage, and it is not clear whether reducing fox abundance necessarily reduces level of damages (except if they can be eliminated entirely).”

That said, the GWT biologists have shown local and seasonal culling of foxes can substantially reduce fox predation on game and livestock, even though the impact on the fox population is only local and temporary. Moreover, many farmers and keepers consider that culling is worth the effort and, as part of a survey of fox control in three areas of England and Wales, GWT biologists Matt Heydon and Jonathan Reynolds found that just over 70% of landowners believed that culling contributed to the suppression of fox numbers throughout their region. Interestingly, the GWT study also revealed that culling seemed to have a beneficial impact on the fox population; the foxes appearing generally healthier and fewer barren vixens in the population. This is presumably a response to a generally less competitive environment. Elsewhere, in 2000, Francesco Frati, Sandro Lovari and Günther Hartl presented evidence to suggest that culling may increase the genetic variability in the fox population. Frati and his colleagues looked at a series of enzymes and mtDNA sequences from six hunted and three non-hunted fox populations in Central Europe and the Mediterranean area, finding that genetic variability was almost absent in the un-hunted populations (i.e. suggesting lots of inbreeding). This suggests that, in some cases, culling may act as a proxy for predation, enhancing the genetic ‘robustness’ of the population by permitting the introduction of new genes (in the form of animals dispersing into the area). The authors speculate that this increased population viability may be one reason why widespread culling programmes (such as those aimed at controlling rabies) have failed to eradicate foxes.

Where possible, it makes more sense to try and exclude foxes from the area, rather than culling them. There are various methods that may achieve this (see Fox Deterrence), although results can vary and may require considerable persistence. Chemical repellents work in many cases, although only those legislated by the Control of Pesticides Regulations (1986) can legally be used in Britain, so the once popular Renardine repellent is now illegal. There have also been some intriguingly novel fox deterrence attempts. Llamas are, I’m told, very efficient at keeping foxes away from livestock and, in August 2011, The Telegraph carried a story about the Abbotsbury Swannery in Dorset who were playing Radio 4 at full volume at the periphery of the swannery to keep foxes away – a tip given to them by a farmer in Devon who apparently uses it to keep his chickens safe at night. The theory is that the sound of human voices is sufficient to keep wary foxes away.

Outside of Britain, many countries engage in fox hunting for control, sporting or economic (i.e. trapping for fur) purposes. Australia, in particular, has gone to considerable effort and expense in a bid to eradicate Red foxes from the country. Since foxes were introduced to Melbourne in 1845 by home-sick expatriates, they have thrived and now occur throughout mainland Australia, excluding northern Queensland and the Northern Territory. The impact of the introduction of the fox to ecosystems in which it had not evolved soon became apparent and it was given official pest status in Victoria during 1894, almost 50 years after the first introduction. In 2004 authorities estimated that foxes cost the Australian agricultural industry in excess of 227 million AUD (£153 million or 183 million EUR) annually and the spread of foxes across southern Australia has coincided with declines in the distribution of several native medium-sized ground-dwelling mammals, including a group of rat-kangaroos called bettongs, the bilby (Macrotis lagotis), and a wallaby species (see Interaction with Species). In recent years Australia has launched a widespread campaign to eradicate, or at least reduce the number of this species, but culling efforts have typically proven ineffective; foxes can withstand high levels of mortality (see Q/A). The control program is also expensive, costing at least an estimated 16 million AUD per year.

Red foxBy the start of the 21st Century, attention had turned to fertility control as a means of reducing the Australian fox population. Work was carried out to assess whether a virus that made foxes sterile could be used, but the project had been largely abandoned by the end of the 2000s owing not only to practical issues of infecting the foxes, but also that this virus would represent a potentially devastating exotic disease for the island’s native possums. Other studies have found that a potent dopamine antagonist called Cabergoline can be added to baits and fed to foxes; the chemical causes abortions and inhibits prolactin production (so the vixen cannot lactate). However sterilisation is achieved, a study by a team at Australia’s Vertebrate Pest Research Unit, published during 2002, reported that there were no significant differences in the survival or dispersal of sterile vixens when compared to fertile ones (i.e. they maintained similar sized territories), suggesting sterilisation is a potentially suitable means of population control for this species. That said, the costs involved as well as the practical difficulties of relying on baits (which have to be found and eaten by your target animal) make any such operations difficult. Consequently, the main form of fox control in Australia is shooting by landowners and hunters, trapping, or poisoning with sodium monofluoroacetate (often known by its catalogue number, 1080). Shooting is labour intensive and often difficult to control fox populations by (as losses are rapidly replaced by dispersing animals). The problem with the latter two methods is their generally unspecific nature – the potential is there for them to kill animals other than foxes, particularly given that foxes rapidly become bait and trap ‘shy’. The 1080 poison, however, is produced by a native plant (pea bushes) and many native species have evolved a higher resistance to the toxin than foxes; this makes it less likely the baits will kill non-invasive species. More recently, biological control has come in the form of the dingo, whose reintroduction seems to be causing a reduction in fox numbers as they’re displaced by the larger native canid (see Q/A). Time will tell how Australia gets to grips with its fox problem.

Back in Britain, in urban areas, complaints of foxes causing nuisance include calling (sometimes at an alarming volume) late at night, setting off security lights, digging up lawns and flowerbeds, raiding bins, killing domestic livestock (especially chickens, ducks, guinea pigs and rabbits), attacking pets (see Q/A) and stealing fruit and vegetables from gardens. Furthermore, they often leave pungent smelling urine and excrement in gardens and occasionally excavate the corpses of buried pets. Fox cubs are also well known to trash gardens during their play sessions, carrying off pot plants, chewing pots, chewing polyethylene play tunnels and plant protection tunnels as well as becoming entangled in garden netting. What's more, adult foxes can squeeze through gaps of only 10 sq-cm (4 sq-in) and easily scale a 2m (6ft fence), making it difficult to totally exclude them from your garden (see Deterring Foxes). Foxes are also often implicated in the loss of dog toys and shoes from the garden. Indeed, it seems that some foxes have developed something of a penchant for stealing shoes and, in October 2009, a forestry worker in the German town of Föhren found a collection of 120 shoes at a fox earth in a wood on his beat – 86 at the earth itself and 32 in a nearby quarry where the foxes had been seen playing.

Despite some valid complaints, foxes do have their benefits. Even to the exclusion of the joy many people get from interacting with them, foxes provide vermin control (preying on mice, rats and pigeons) and run a litter clean-up service in urban areas by eating discarded food. In rural areas, fox feed heavily on rodents and rabbits that can be considerable pests to farmers. Scottish naturalist James Lockie estimated that a fox could eat at least a thousand voles each winter, saving the famer a potential 10.5kg (23 lbs) of grass (i.e. sheep/cattle food). It is very unlikely that foxes could actually control the populations of either rodents or rabbits in rural Britain, but they do represent a significant source of mortality for both groups. In their contribution to the 2003 compendium, Conservation and Conflict: Mammals and Farming in Britain, David Macdonald and his co-workers (including Jonathan Reynolds from the GWT) used the 1997 grain price to calculate, all other inputs ignored, that a farmer about to shoot a young fox, newly recruited into the rabbit-eating population, could forfeit between £156 (in 1997, about 250 USD or 225 EUR) and almost £900 (almost 1,500 USD or 1,300 EUR) in saved grazing – in other words, depending on the population density of rabbits, the number of rabbits the fox could take could eat some £900 worth of the farmer’s crop. Overall, the biologist concluded:

If we apply the calculations presented above and ignore other inputs, total national annual saving of approximately £30-£150 million [49-246 million USD or 43-216 million EUR in 1997] worth of crops thanks to foxes killing rabbits would be suggested.

Obviously these are calculations based on a whole host of variable factors, and it is a complex task to weigh up economic benefits of culling one species to protect another. What these figures do, nonetheless, is suggest that foxes have the potential to be beneficial to farmers as a form of pest control. (Back to Menu)

Domesticated fox cubMan’s best friend? Fox domestication
While it is true to say that many people see the Red fox as vermin to be controlled or eradicated, equally as many (if not more) see it as a beautiful animal that typifies all that is considered wild. A select few of these people have wanted a fox as a pet. Unfortunately, what I shall refer to as “un-tamed foxes” (i.e. those rescued, or taken from the wild as cubs and raised as adults) typically do not make very good pets – the cubs can be very destructive and foxes have an odour all their own, which can be difficult to deal with. The result is that many who try find themselves out of their depth and this can result in the animal being abandoned. Caroline Vale, who runs Vale Wildlife (a wildlife rescue centre in Gloucestershire), tells me she has found a fox wearing a collar walking around a local park ‘looking lost’. Consequently, I cannot advocate any attempt to keep an untamed fox as a pet (see Q/A). The problems associated with raising a fox have not, however, put some off trying. (Photo: A 3.5 month-old cub bred by the Fox Domestication Project -- see below -- as part of a study to better understand the impact of domestication on appearance and behaviour.)

Wallen, in his book Fox, noted that attempts were made to domesticate (presumably Fennec) foxes during the dynasties of the Old Kingdom of Egypt (2700 – 2159 BC); it is believed that the aim was to keep the foxes as a source of meat and fur. Wallen pointed out, however, that most attempts to domesticate foxes have failed, although he noted that some hunts have kept ‘pet’ foxes and he printed a photo of a fox chained to the bumper of a car in rural Minnesota circa 1940. In fact, recent archaeological evidence from the Middle East (northern Jordan) found at least two graves, dating back some 16,500 years, where foxes appear to have been buried with humans. In a recent paper to the journal PLoS One, a team of archaeologists fronted by Edward Banning at Toronto University speculate that the placement of the fox remains within one particular grave indicates that the fox was a companion animal to, rather than an adornment of, the person buried there. The researchers conclude that:

Although we may never be able to reconstruct the nature of the relationships between humans and early domesticated dogs (were they pets or work animals, or both?), their inclusion in burials reveals ties of emotional consequence. It is possible that the burial of a fox with a human might have had the same social, ideological or symbolic significance as that of a human with a dog.

Whatever happened in these early civilisations, it wasn’t until the mid 20th Century that we saw the first scientifically controlled attempt to domesticate the Red fox – this came in the form of the ‘Fox Farm Experiment’. The experiment, the goal of which was initially shrouded in secrecy owing to restrictions on the study of Mendelian inheritance at the time, has provided a fascinating insight into how physical and behavioural traits are linked, and provides a fantastic example of how artificial selection operates. I will only summarise the situation here, but those interested in learning more are directed to a fascinating overview by Lyudmila Trut published in the March-April 1999 issue of American Scientist and, more recently, the article by Evan Ratliff in the March 2011 issue of National Geographic (see Recommended Reading).

In 1958, Institute of Cytology and Genetics (part of the Siberian Department of the Russian Academy of Science) biologist Dmitry Belyaev and his graduate student Lyudmila Trut started scouring fur farms in the (now former) Soviet Union looking for silver foxes -- a colour variant of the Red fox -- to use in their experiment. Belyaev and Trut selected foxes that showed the least fearful and aggressive response to humans for their experiment and, in all, the researchers collected 130 animals (100 vixens and 30 dogs), most from a farm in Estonia. Recent molecular data has traced the origins of these foxes to one of the earliest fur farms (established in the 1890s) on Prince Edward Island in south-eastern Canada, which caught many wild foxes locally for farming. In 1959 the researchers began selectively breeding them for sociable traits – in other words, they bred only the most sociable (i.e. friendliest) animals in each litter. When the cubs reached sexual maturity (at 7-8 months) they were scored on their tameness: Class III foxes fled or tried to bite when touched; Class II foxes let themselves be stroked and handled but showed no emotionally friendly response to humans; while Class I foxes were friendly to humans, wagging tails and whining. In the fourth generation (1964) cubs were born that didn’t show any aggression towards humans and some cubs would also wag their tails. By the sixth generation, the researchers had to add a fourth class (Class IE or ‘domesticated elite’) to account for foxes that were eager to establish human contact by one month old, whimpering to attract attention and sniffing and licking the humans like dogs – some would even jump into the arms of their keepers and lick their faces. In the sixth generation just fewer than 2% of cubs were Class IE; this had risen to 18% by the 10th generation, 35% in the 20th generation and, by the late 1990s/early 2000s 70% or more of cubs fell into Class IE. In short, not only had the geneticists created foxes that weren’t afraid of humans, but they actively wanted to bond with people.

As the experiments continued the researchers witnessed an explosion of changes in external appearance and, by the 1980s, not only were they seeing a change in the foxes’ temperament and sociability, they were also seeing changes in their appearance. Indeed, one of the first traits they saw emerge was a change in the coat colour; cubs started appearing with white (pigment-less) patches on their fur. Genetic work revealed this ‘piebalding’ (which is common in domesticated animals) was caused by a mutated copy of the Star gene. Coat colour was, however, only one of several traits that began appearing. Back in 1866, in his book The Variation of Animals and Plants under Domestication, Charles Darwin described how domesticated animals tended to share a set of common characteristics that make them appear juvenile: they’re smaller in size, have less rigid (i.e. ‘floppier’) ears and curlier tails than their non-domesticated progenitors. This is a phenomenon known as paedomorphism (a type of neoteny) and it was precisely this that the Russian biologists were seeing on their farm after only nine generations. They were also seeing a widening of the skull and shortening of the snout – as Alexandra Horowitz put it, in her 2010 book Inside of a Dog, the foxes are “improbably cute”. So, in selecting for only a single trait (i.e. a calmer temperament), the biologists were seeing the incidental development of a suite of other puppy-like features, suggesting that the traits are genetically linked. Indeed, DNA analysis of some of the farmed animals is showing that domestication is a complex phenotype (i.e. is the result of a suite of genes, rather than a single gene), with the farmed foxes differing from un-tamed animals by 40 genes.

Domesticated silver foxThe finding that many of the features we associate with domestic dogs may have arisen purely as a result of selecting for friendly animals was striking in itself, but the researchers wanted to know how much of a fox’s temperament was ‘hard-wired’ – i.e. how much was nature and how much nurture. The results were surprising. In a separate building on the same farm, the researchers were also breeding foxes, but this time they were selecting for aggressive traits, resulting in a collection of foxes that were highly aggressive towards people approaching their cages. When the researchers removed a cub born to an aggressive vixen and placed it with a tame vixen, the result was still an aggressive adult. This suggests that aggression in foxes may be more a result of their genes than the kind of up-bringing they experience. Why should this be?  Well, research into the hormone profiles of the farmed foxes has shown that they have altered levels of three key hormones in their brains: serotonin (reduces aggression); noradrenalin (a stress hormone); and dopamine (involved in stress regulation and sociability). Farmed foxes have higher levels of serotonin in their brains than non-domesticated ones, while levels of noradrenalin and dopamine rise later in development, causing a delay in the fear response. Indeed, the researchers found that the fear response develops in dogs at eight-to-12 weeks old (depending on breed), while in un-tamed fox cubs it appears after only six weeks – in domesticated fox cubs, however, there was no sign of the fear response even after nine weeks. It seems that in un-tamed foxes there is a rise in stress hormones between two-and-four months old, reaching a peak around sexual maturity (eight months); in domesticated foxes this rise is delayed by several weeks. The biologists suggest that this -- coupled with the fact that, on average, domesticated fox cubs start responding to sounds two days earlier than non-domesticated ones, and open their eyes a day earlier -- provides a longer ‘window’ during which the cubs can bond with their carer. (Photo: An adult fox bred as part of the Russian domestication project, showing the curly tail characteristic of dogs and domesticated foxes.)

Another striking finding from the fox domestication experiments comes from preliminary behavioural experiments conducted by Brian Hare at Duke University in North Carolina. Hare studied the ability of the farmed foxes to act on social cues from humans. As most dog owners will be only too aware, domestic dogs have a superb ability to respond to our moods and have evolved the ability to follow pointing and eye movements to objects (something that human babies don’t get until about a year old). Hare found that tamed fox cubs were as good at following human points and eye movements as puppies of the same age. In other words, the researchers set out with the goal of breeding a tame fox, but by selecting only for this trait they ended up with what is, for all intents and purposes, a domestic dog in appearance and behaviour. Indeed, in Ratliff’s article, Cornell University geneticist Anna Kukekova said the foxes reminded her of Golden retrievers: they don’t know that there are good and bad people, or who they’ve met before, but treat every human as a potential companion. The research by the Institute of Cytology and collaborating organisations has provided a detailed and striking insight into the process of domestication and has shown that, although it doesn’t happen spontaneously, it can happen quickly (in only 50 years).

The fox farm project is still running, although it has suffered some setbacks -- largely in relation to funding -- in the run-up to (and since) the collapse of the Soviet Union in 1991. Much work has, nonetheless, been published lately regarding how to improve the living conditions on fur farms, in terms of stimulation for the foxes and social housing of the animals. According to Ratliff’s article, the researchers are currently trying to obtain permits to sell some of their surplus tame foxes as pets, for which there is a growing market, particularly in North America. The SibFox Inc website (run by the Institute of Cytology) suggests that foxes are already available for purchase from the farm, although some prices I have seen quoted go as high as 6,000 USD (£3,800 or 4,600 EUR) per fox. Some species of fox (including Red and Fennec) are also widely sold by pet retailers in North America and elsewhere; it seems to be becoming more common for people to own a pet fox. Even where foxes have been domesticated and sold as pets, however, some still possess a few ‘wild’ traits and most contain a full compliment of scent glands, which can cause problems for their owners. I have read of some people trying to get the scent glands on their fox surgically removed, with varying success. (Back to Menu)

Hand-feeding a foxLiving with the wild: interacting with wild foxes
Not everyone has four grand to spend buying a domesticated farm fox and, as such, are restricted to watching wild animals. Getting even a glimpse of a wild rural fox can be frustratingly difficult (and I speak from considerable personal experience there!) but fortunately, for those who appreciate being able to see these mammals, foxes have readily taken to our towns and cities and are now frequent visitors to our back gardens, whether we realise it or not.  Foxes began living in our cities after World War I; a response, many people consider, to a change in people’s lifestyles. There has been some suggestion that an outbreak of myxomatosis in Britain during the early 1950s actuated the fox’s colonisation of urban areas, although the current evidence doesn’t support this theory (see Q/A). Stephen Harris and Phil Baker at Bristol University consider that the most likely "cause" of urban foxes was the development of once rural land after the First World War; land was built upon and, rather than moving, the foxes adapted to their new surroundings. Whatever the ultimate reason for foxes appearing in our towns, they have thrived in this environment and shortly after World War II they became commonplace (DEFRA, at the time known as MAFF, shot 181 foxes in southeast London during 1947!).

My experience, and that of many others, is that foxes readily become used to human activity and learn to ignore it (although I would not go as far as to call them “tame”, a mistake many people seem to make – wild foxes are just that, wild, regardless of how relaxed they appear in your company). In fact, they can become so un-phased by (almost complacent of) human activity that they have been seen in busy high streets during the daytime, they wander around an industrial estate near me in the middle of the day ignoring the cars and workers, and scavenge on rubbish tips dodging lorries. The most extreme example I have come across is a fox letting a child play with her cubs. In a short paper, on the spread of the fox in the London area, to the journal Ecologist, Ian Beames described how, during 1969, a family of fox cubs spent some time playing with a five-year-old girl and her ball in a Surrey garden, as the vixen sat quietly watching. Such behavioural plasticity (i.e. the ability to rapidly alter your behaviour to make the best of a situation) means that with a little patience they can be easy to watch. Often food is required, even if only initially, to win the fox’s trust and give it a reason to hang around in the garden/area. In some cases, the fox may come to expect a hand-out (which is why you should never hand-feed a wild animal). One fox I had the pleasure of watching in Horsham, West Sussex several years ago, was known to wait under the same tree at a specified time every night for the owner of an adjacent house to supply her supper (of dog food). Apparently, on one occasion when the waiter was engaged for longer than anticipated and failed to meet the 9pm feeding, the fox crossed the road, went into his front garden, put its paws on the window ledge and peered into his lounge!

I have frequently heard it said that feeding foxes is a bad idea, usually based on two lines of reasoning:

1. Foxes will become dependent upon the food source and starve if said food is removed;

2. Foxes fed by humans are likely to readily lose any fear they have of people and may even approach strangers looking for food (never a good thing for a wild animal!). While personal observation and anecdotal evidence seems to support the latter notion, given the terrific adaptability of Red foxes, it seems unlikely that they would become dependent on any single food source. Ecologically, monophagy or stenophagy -- i.e. those that only eat one (or a very narrow range of) thing(s) -- is generally considered a recipe for extinction – after all, if you only feed on a single species and that species dies out, so do you. By contrast, if you are able to switch your tastes to cover a wide range of food items (i.e. are polyphagous), if one item declines in availability you can switch to another (assuming they don't all decline in concert!). As we’ve already seen, foxes have one of the most catholic diets of any mammal. The subject of feeding wildlife (and its associated pros and cons) is discussed in a separate Q/A.

Overall, I would conjecture that if you want to feed foxes in your garden, there are a few simple guidelines you should take into consideration:

1. REMEMBER that not everyone shares your appreciation of foxes (or wildlife in general). Neighbours with small livestock that are housed outside (e.g. chickens, rabbits, guinea pigs, etc.) may be especially unimpressed by your fox-feeding activities. It is also worth bearing in mind that food taken from your garden may be buried in your neighbour's garden!

2. DO NOT feed highly processed foods (crisps and snacks), especially NOT chocolate (see Q/A for a discussion of this). I have heard stories of people buying cream cakes and chocolate gateaux for their foxes; these should be avoided.

3. DO NOT feed too much. You don't need to put out lots of food and are arguably better off just scattering some dog biscuits around the garden. Lots of food in one area could cause the foxes to reduce their activity and concentrate any disturbance (digging, scat, etc.) in a smaller area.

4. DO spread the food around; this will increase the time the fox will spend in your garden as it collects all the food and reduces the potential for aggressive encounters if you have several foxes visiting at the same time.

5. DO feed them foodstuffs that they are more likely to encounter while foraging naturally (i.e. raw or cooked meats, fruit and berries, vegetables, eggs, earthworms, etc.); feeding of canned dog food is also an option.

6. DO put out water, which is often more important to the fox (and many other garden mammals) than the food itself.

7. DO NOT encourage the foxes to take food from your hand, or to come into your house for food.

My preferred method of watching foxes in a garden is to scatter a couple of handfuls of biscuits around the garden and sit inside the house (or, being an amateur photographer, in a hide/shed) to await the fox’s arrival. The scattering prolongs the fox’s visit and, by not being in the garden, there’s no risk of the fox associating me with the food.

Be aware that putting out food for foxes can lead to changes in territory size -- even the halving of territory size in some urban areas -- and numbers. In northwest Bristol, Stephen Harris and his colleagues observed a positive feedback loop with regards to householders putting out food for foxes and the number of fox sightings. The biologists found that as the number of people putting out food increased, more fox sightings were reported and more food was put out, leading to each given patch being able to support more and more foxes. At one stage (before mange arrived), Harris and his co-workers recorded 30 adult foxes per square kilometre – the highest density of foxes ever recorded!

Ultimately, foxes are in our towns and cities to stay and we have two choices: we can learn to live with them, or we can opt for a never-ending all out war on them in a (in my opinion, futile) bid to eradicate them. I know on which side of that particular fence I sit. (Back to Menu)

Fox climbing fenceInteraction with other Species: Foxes interact with a large number of species in a variety of different ways. Some of these interactions are obvious (Red foxes are predators and, as such, they eat other animals) while others may be more subtle: the construction of earths, for example, changes the habitat and influences the plant communities in the vicinity. That which follows is a series of summaries of the ways in which foxes interact with a variety of species with which they share their environs. One question that is frequently asked, but deceptively complicated to answer is what impact -- if any -- foxes have on the populations of their prey. In other words, can foxes control the numbers of their prey?  I shall touch on this subject briefly below, but suffice to say that many factors interact to complicate the picture; of these factors, habitat plays a crucial role.

In a recent paper to the journal Mammal Review, a team of ecologists headed by Lucrezia Gorini at the University of Rome reviewed the impact that habitat heterogeneity (i.e. how diverse the habitat is) has on how predators interact with their prey. Gorini and her colleagues note that how variable a habitat is can influence the relationship between a predator’s search and kill rates. To put this into perspective, imagine you throw a marble onto the ground and then have to search for and recover it: if you’re standing on a pavement (a nice flat, uniform surface) the marble is going to be easier to recover than if you’re standing in a woodland, which has leaves, grass, flowers, fungi, trees, etc. to get in the way and obscure the marble. The same is true of a predator searching for its prey – the type of habitat in which it’s hunting can drastically affect how easy it is to find and (perhaps more crucially) sneak up on the prey. So, what we see is that habitat heterogeneity can change the form of the functional response (i.e. the relationship between predation rate and prey abundance) – making a difference between the total number of prey in the ecosystem and that actually available to a predator. We can add to this equation the behavioural response of the prey; they may avoid a particular area if they perceive that they’re more at risk of attack there, further reducing a predator’s chance of securing a meal. I hope I haven’t lost you by this point, but if I have don’t worry: the aim of this section is not to debate the pros and cons of theoretical models of predator-prey interaction. In fact, I don’t plan to make any further mention of the theory. The foregoing is simply meant to illustrate why scientists often have a hard time providing a definite answer to the question of whether a predator can regulate the abundance of its prey. The result may be that foxes can control, for example, vole numbers in some habitats but not in others, or in some seasons but not others (e.g. in summer when they can hear the voles rustle in long grass, but not in winter when the ground’s covered with snow). (Back to Menu)

European RabbitSmall and Medium-sized Mammals
We have seen that foxes can have positive economic benefits to farmers by eating pest species such as rats, mice, voles and rabbits, but the question remains whether they can eat enough of these to control, or even reduce, their populations. Back in 1970, Australian biologist Ken Myers suggested that foxes could indeed have such a regulatory impact on prey (particularly rabbit) numbers, and several studies suggest that foxes can cause a decline in gamebird populations. Until comparatively recently, however, this theory hadn’t been empirically assessed – this changed in the 1980s.

There is now some evidence that foxes can control the populations of certain prey species, although typically only after the numbers have first been reduced by something else (e.g. human persecution, disease, disaster, etc.). On the Yathong Nature Reserve in New South Wales, Australia during the early 1980s, for example, Alan Newsome and his colleagues found that predators -- i.e. foxes and feral cats -- maintained rabbit (Oryctolagus cuniculus - left) numbers at a relatively low level only after a severe drought caused an initial die-off. Newsome and his co-workers observed that rabbit populations exploded, following the breaking of the drought, in areas where foxes and cats were continually shot; after just over a year, rabbit numbers in the predator controlled zone had risen by 12%. In parts of the reserve where foxes and cats weren't controlled, by contrast, the rabbit population had only risen by just under 3% during the same period, suggesting that the foxes and cats were keeping the population at a low level. Similarly, around the same time, former MAFF biologists Roger Trout and Andy Tittensor concluded that predator pressure on wild rabbits in England and Wales may limit increases in density, but only after numbers have been initially reduced by some other factor. In other words, if something acts to reduce rabbit numbers, foxes can keep the populations low, but they can't cause a reduction in rabbit numbers.

A similar situation is seen in rodent and vole populations. In south-eastern Australia, for example, foxes have had little impact on the plagues of House mice (Mus musculus) that periodically cause millions of dollars of damage to agricultural crops. Similarly, in Sweden a dramatic decline in fox abundance, resulting from a sarcoptic mange outbreak, failed to have any discernable impact on vole numbers. In Britain, Aberdeen University zoologist Declan O’Mahony and his colleagues considered that foxes should have a strong stabilising effect on vole populations but that they do not appear to influence the three-to-four year 'boom' and 'bust' population cycles that we see in these rodents. The reason foxes don’t appear to make much of a dent in the vole population is almost certainly because these rodents are prolific breeders. Indeed, in his 1980 book The Red Fox, Huw Lloyd notes that voles can survive mortality rates as high as 92% (i.e. only 8% of the population needs to survive to breed the following spring); in years of low productivity, foxes may take some 40% of the vole population but in ‘boom’ years they cannot take more than about 3%. Lloyd concluded:

Generally, what evidence there is indicates that the fox’s predatory role is of little significance in limiting the numbers of its main prey foods. It may, however, have an important effect on certain prey species in certain circumstances.”

More recently, during the mid-1990s, former Bristol University biologist Phil Baker and his colleagues studied the impact of foxes on various prey species on an organic farm in Wiltshire, arriving at much the same conclusion as Lloyd. Baker and his co-workers found no evidence that foxes were single-handedly regulating the populations of rabbits, Bank voles (Myodes glareolus) or Wood mice (Apodemus sylvaticus). The authors did, however, point out that, although foxes alone cannot control vole populations, such regulation is possible when the impact of other predators is considered: one study found fox, kestrel, weasel and feral cat predation accounted for 85% of vole mortality. Despite the foregoing, however, there are some reports implicating foxes in the control of some rodent populations and, in The Nature of Foxes, Rebecca Gambo tells how the removal of foxes in Wisconsin caused an explosion in the mouse population that led to the reinstatement of the predator. Such examples are presumably the exception, rather than the rule. The situation is probably further complicated by observations that some rodents appear able to change their activity patterns to reduce the risk of being caught by a fox. In a paper to the Journal of Mammalogy during 1995, for example, Michael Fenn and David Macdonald reported that Norway rats (Rattus norvegicus) using a midden in Oxford’s Wytham Woods became strictly diurnal (i.e. active during the daytime) in the summer when the risk of fox predation was lower; when the threat was removed -- by enclosing the area with a fox-proof fence -- they reverted to the nocturnal activity normally observed in this species. So, the rats were altering their activity to make it less likely they would encounter a fox.

The situation of the fox and the Brown hare (Lepus europaeus) is a complicated one. Many authors consider that foxes rarely take hares, while some studies suggest that they may be significant predators locally. In their 2010 Mammal Society booklet, The Brown Hare, Stephen Tapper and Derek Yalden succinctly summarise the issue:

Although a fit adult hare has little to fear from a fox, it does not follow that fox predation is unimportant to hares. Foxes seem to have a big impact on hare populations because they kill leverets [baby hares]. A study in East Dorset showed that brown hares formed about 11% of the foxes’ diet, year-round, although this was an area where hares were not very numerous. From the numbers of foxes and brown hares, it was estimated that each fox killed about 50 leverets each year.”

Indeed, the influence that foxes have on Brown hare populations is interesting. It has long been considered that foxes can detrimentally impact hare populations, with low hare numbers in areas with high fox densities. Britain’s hare population was probably at its peak during the early 1900s, when foxes were relentlessly persecuted by gamekeepers and has generally declined in the post-war years, although this may equally be a response to a change in farming practices as much as a reduction in the numbers of gamekeepers (and hence fox control). Research by the Game and Wildlife Conservation Trust (GWCT) has demonstrated that, in some regions at least, killing foxes can lead to an increase in hare populations and, in 1995, GWCT biologists Stephen Tapper and Jonathan Reynolds used a computer model to assess what would happen to a hare population if foxes were completely eliminated. Tapper and Reynolds’ simulation suggested that, if foxes were removed, there would be a three- to six-fold increase in hares. Similarly, there is a noticeable correlation between areas with high levels of gamekeeper-led fox control (e.g. in much of eastern England) and increases in the hare population. Of particular importance seems to be the relationship between the peak of fox control, which is in the gamebird nesting season (April-July), and hare numbers; this period also corresponds to the peak period for the birth and growth of leverets. Curiously, however, some authors have observed a different response on certain study sites. Stephen Harris and Phil Baker point out, in their contribution to Mammals of the British Isles, the increase in foxes in East Anglia hasn’t been paralleled by a decline in hares.

European Brown HareThere is some evidence that season may have an important influence on the impact of foxes on Brown hare (right) populations, and a study in western Poland between 1996 and 2002 found that culling foxes had the greatest impact during the autumn and winter. Presumably in this case the combination of fox dispersal (autumn) and increased movement around the breeding season (winter), coupled with hares being more exposed (lack of vegetation) is significant in explaining this relationship. There is also some suggestion that hare behaviour may also reduce the potential for fox predation. In a rather obscure 1953 German paper D. Müller-Using described ‘three-toed walking’ by hares in the presence of foxes. More recently, Anthony Holley studied Brown hares living in the Somerset Levels in southern England between 1977 and 1987 and found evidence suggesting that they signalled to approaching foxes they had been spotted by standing on their hind legs and facing the stalker – this they did 31 out of 32 encounters he saw. Holley noted that the hares didn’t do this when domestic dogs approached (suggesting it was a response to a known predator) although, in a 2007 paper to the New Zealand Journal of Zoology, John Flux described similar behaviour towards a cat that entered a field of hares he was watching. The idea, it seems, is that the hare stands up to signal that it has seen the predator and that there’s no point in the predator attempting a chase.

Finally, it appears that, although foxes may not be able to influence the cyclical nature of vole populations, they may transfer this ‘cyclicity’ to the populations of other species, such as hare and grouse. In a 1994 paper to the journal Ecology, Swedish biologist Erik Lindström found that predation on these other species was higher in years when vole populations were low. Intriguingly, when the Scandinavian fox population crashed as a result of the mange epidemic, Lindström observed that this ‘cofluctuation’ (e.g. high vole population, high hare population) disappeared, suggesting that the foxes were responsible for it. In other words, the foxes preferentially took voles but when numbers dropped they turned their attentions to other species causing their populations to fluctuate in a similar manner. When voles were abundant, for example, few hares were taken and so numbers remained high, but when vole populations crashed more hares were taken, causing a decline in their population. Lindström thus concluded that fox predation was a crucial factor in limiting the numbers of hare, grouse and deer kids (in the autumn) and in conveying the vole boom-bust cycle to small game species. (Back to Menu)

Cow with calfLivestock
It is their attacks on man’s livestock that has probably contributed more to the fox’s status as a pest than any other interaction. Foxes are well known to take lambs, young goats, chickens, geese, and piglets if the opportunity arises – there are also sporadic reports of foxes trying their luck with mature sheep, calves, pony foals and even full-grown cows! Indeed, in his book Town Fox, Country Fox,, Brian Vezey-Fitzgerald talked about a remarkable crop of sensational stories that made the press during the very harsh winter of 1963; one, in the Farnham Herald, told how a pack of foxes chased a four-foot-tall bullock before it was cornered in a ditch and “torn to pieces”. Vezey-Fitzgerald noted that this scene was reconstructed from footprints in the snow, rather than first-hand testimony and thus considered what actually happened was the bullock missed its footing and fell into a ditch, whereupon it died of hypothermia, and the carcass was visited by foxes. Whatever really happened (and my inclination is to side with Vezey-Fitzgerald on this), it illustrates the point that foxes are seldom seen taking livestock; instead they are assumed to have been the culprit. There can be no argument that, at a local scale, foxes have the potential to cause significant losses, but how significant they are to the national livestock industry is a highly contentious issue.

In his 1940 classic, I Bought A Mountain, Thomas Firbank says that a considerable number of lambs are killed by foxes in the hilly grazing land around Snowdonia, although the published evidence is rather sparse. In his 1984 contribution to the Journal of Applied Ecology, Ray Hewson at Aberdeen University studied the diets of foxes in two areas of western Scotland. Hewson, by contrast, found that foxes in these areas fed primarily on sheep carrion and field voles, supplementing their diet by killing about 1.3% of the lambs estimated to have been born in the area during 1976. Hewson provided minimum values for lambs killed of 1.8%, 0.8% and 0.6% of the lambs estimated to have been born in 1977, 1978 and 1979 respectively. The paper reports that foxes (and eagles) killed lambs of one to five days old and in apparently good condition; foxes took lambs up to 10 kg (22 lbs) in weight, while eagles only took lambs as heavy as 6 kg (13 lbs). Hewson observed several other trends -- such as foxes consuming more carrion in the first half of the year and more field voles in the second -- and speculated that, with regards to lamb susceptibility to foxes, lambs of ewes breeding for the first time (compared to those of older ewes) may have been more vulnerable owing to poorer maternal care. A similar study in Wales found that sheep carrion was an important food source for the foxes during the summer (found in about 40% of stomachs) but evidence for direct predation was lacking.

In his book, Running with the Fox,, David Macdonald is of the opinion that foxes only rarely take lambs and, while tracking foxes in the lambing fields of the Cumbrian Fells, he found that they appeared disinterested in the lambs, sprinting after rabbits in the same fields. The foxes did, however, consume afterbirth and appeared to eat the lambs’ dung, presumably because the milky faeces of young lambs are rich in undigested fats and proteins. In the territories of two vixens on Orton Scar, Macdonald found a total of four lamb carcasses that had been partially eaten by foxes; two showed no sign of bleeding and were presumably dead before the fox took them. Macdonald readily accepts that he may have missed some corpses, but found no evidence for any substantial consumption of lambs that year:

Considering the number of foxes in most areas, if most of them killed lambs habitually the losses would be astronomical. Since they are not, I presume that most foxes rarely or never kill a lamb.

Macdonald suggested that, as lamb/sheep carcasses are left out to rot (often visited and defecated on by foxes, but rarely eaten) and the vixens he watched were dodging lambs in the pursuit of rabbits as though the lambs were obstacles rather than food, lamb is probably not a preferred food for most foxes. The geographical difference in lamb predation rates, Macdonald considered, probably reflects the availability of other, more desirable, prey. Indeed, Macdonald’s captive studies in Oxford seem to provide some support for this theory; his foxes refused to eat the lambs he presented to them unless nothing else was available. This doesn’t, however, explain why foxes appear to relish the after-birth, withered tails and testes that drop off ‘branded’ lambs. Of course these observations represent one population in a single year, but they certainly imply that not all foxes are lamb-killers – a conclusion that many farmers and gamekeepers have also come to. During a series of detailed observations of foxes among lambing ewes in Australia, for example, both G. Alexander and colleagues (writing in 1964) and Peter Mawson with the late John Long (in 1989) described how foxes were generally wary of newborn lambs, but that at least one individual was observed to attack and kill a healthy lamb. In addition, subsequent work by Australian biologist Ian Lugton (see below) suggests that mature male foxes are more likely to prey on lambs than either females or juvenile animals. This implies that there may be certain 'problem' foxes that may be more likely to take lambs. Indeed, such ‘rogues’ are frequently reported by landowners, who describe animals that appear to learn how to tackle chickens and lambs; when these animals are removed the losses stop, even though there are other foxes in the area.

Ewe with lambIn Australia, Carolyn Greentree and colleagues at the Vertebrate Pest Research Unit in New South Wales found that fox predation was the probable cause of death for a minimum of 0.8% and a maximum of 5.3% of the 1,321 lamb carcasses they examined. In their paper to the Journal of Applied Ecology, the biologists report that fox control three times per year reduced the maximum percentage of lamb carcasses attributed to foxes from 10% to just fewer than 4%. Other studies in Australia have produced similar figures: foxes killed 3-4% of the healthy lambs and, in one study, a substantially higher proportion (17%) of sick/starving ones. Indeed, lambing indoors significantly improves survival of the offspring by not only removing the threat from predators, but also providing immediate assistance from a farmer in the case of trouble. The timing of any fox control can also have a sizable impact on lamb survival. A huge study of fox control in Australia, for example, found that fox predation on lambs was significantly reduced if culling was carried out twice per year -- during the autumn and again in late winter or early spring -- and farms operating a ‘good neighbour’ policy (i.e. each controlling foxes on their land) had fewer lamb losses than those that didn’t.

Also in Australia, Lugton studied the diets of 212 foxes from south-west New South Wales between 1985 and 1989 – he found sheep remains in 31% of cases, with fresh newborn (i.e. up to a month old) lambs identified in just fewer than 4% of all stomachs on average. This average, as is often the case, masks regional variation and Lugton noted that evidence of lamb consumption was ten-times greater (i.e. 35%) among foxes collected near (i.e. within a kilometre) lambing flocks. Lugton concluded that where fox density was high, with a high proportion of older animals in the population, and alternative preferred food (particularly house mice) was scarce, lamb predation was likely to be severe. Subsequent to this, Lugton autopsied 172 lambs, most less than three days old, between April 1985 and the spring of 1992 and found that, of the 131 for which a cause of death could be assigned, 40 (23%) were considered to have been killed by foxes. Of these lambs, 15 (11%) were in apparently good condition -- i.e. had primary fat reserves intact -- while the other were either very thin or too damaged to be able to tell. The bulk (58%) of dead lambs died after they failed to suckle.

More recently, Rebecca Moberly and four of her colleagues at Bristol University surveyed sheep farmers across the UK about the levels of fox predation on lambs. The results of their questionnaire -- published in the journal Wildlife Research in 2003 -- showed that, although individual losses were low, the range of "perceived" losses to foxes was high: 0.0008 to 0.26 lambs per ewe (i.e. 1 lamb lost per 1,250 ewes to 1 per 4 ewes). The paper also reports that fox predation was more likely to have occurred on larger farms and that 59% of those who responded to the survey had reputedly lost at least one lamb at their most recent lambing. As in Australia, the researchers found that indoor lambing was an important preventative measure against fox predation.

So, what does the above mean for the farmer? After all, knowing that foxes don’t appear to take many lambs is no consolation if you’re losing lambs. Well, one Cornish farmer I was talking to last year (2011) told me that he started culling foxes on his land when he lost a lamb – he explained that it was essentially the same as taking £100 (120 EUR or 160 USD) out of his wallet and setting fire to it. Obviously this cost has to be weighed against the costs of fox control, but as most farmers will cull foxes themselves it generally has little perceived direct cost, and many farmers consider it worthwhile. How much these losses cost the sheep industry as a whole remains something of an unknown. A study of Blackface lamb production in the Scottish Hills between 1993 and 1996 estimated that foxes took 1.5% of the total potential revenue on one farm and 0.6% on another – this equated to, depending on the year, £75 to £300 (90-361 EUR or 118-474 USD) for the first farm and £34 to £134 (41-161 EUR or 54-212 USD) on the second. I know of no similar figures for English or Welsh lamb production.

CockerelMany poultry losses occur on residential holdings (i.e. people who keep chickens in their back garden or on their allotment) and, as such, there are no figures for the numbers killed or the estimated cost. There are some cases, however, where chickens are taken from farms and, a survey by the GCWT found that, among farmers with free-ranging poultry, half to almost 80% of respondents reported losses in the year leading up to being questioned; occurrence roughly mirrored fox abundance (the fewest cases in west Norfolk, while the east Midlands had the most). The GWCT also found that the presence of a gamekeeper significantly reduced the likelihood that poultry would be lost, although secure fencing/housing should also be employed where practicable. Indeed, according to a 2004 study, published in Veterinary Record, by Moberley and her colleagues at Bristol University on fox predation of free-ranging poultry flocks in Britain:

"… changes in farm management would be the most cost-effective means of reducing fox predation, rather than greater fox control"

It seems that, of the farmers surveyed, egg producers reported losing the most birds; up to 77.6% in one case. Overall, however, the average reported mortality across the sample was less than 2%, but with significant local/individual variation. It is worth remembering that averages tend to ‘smooth out’ the perceived risk for any individual stakeholder. If, for example, there are 10 farms in an area and a total of 10 lambs taken in that area over the year, the average is a single lamb per farm while in reality all 10 could’ve been lost from a single farm and the other nine didn’t suffer any losses. This just reinforces the need to be careful when using such statistics.

Unfortunately, the same data for predation by foxes on piglets and goats do not exist and, although foxes have been reported to carry piglets away from farms, such accounts are largely anecdotal and it is not clear whether the fox took a live piglet or scavenged a dead one. The only study I’m aware of was conducted by D.F. Richards in Devon during the early 1970s. Richards found piglet remains in 4% of fox scats that he examined but, upon liaison with local farmers, all cases were tracked back to dead animals buried in an orchard and subsequently exhumed by the foxes. In his 1977 paper to the Journal of Zoology, Richards explained:

No live piglets could be proved to have been taken by foxes, although on one occasion a fox was seen in a farrowing house.

Obviously, ‘could not prove’ and ‘never happened’ are two different concepts, but it serves to highlight the paucity of data on this subject.

The only study I am aware of looking at fox predation on goats was conducted in western Australia by John Long and colleagues at the Agriculture Protection Board during the 1980s. Long and his co-workers report, in their 1988 paper to the Journal of Agriculture Western Australia, that foxes were assumed to have killed 16 (6%) of the 257 Cashmere goat kids in their study. Kids less than three-months-old were most at risk, and were killed by bites to the abdomen and pelvic region. (Back to Menu)

Common PheasantThere can be little doubt that foxes have the potential to impact the game harvest, not least because they will take 'sitting' birds (i.e. females on eggs), which results in the death of the hen and her offspring. Generally speaking, linking fox predation with declines in a gamebird species is difficult – it’s hard to be sure that it was the fox that caused the decline and it wasn’t just part of a bigger picture. Similarly, it can be difficult to find any correlation between fox numbers and losses to the game population. Perhaps the most detailed assessment of the role predators have on the game harvest comes from work done by the GWCT as part of a six year study on Salisbury Plain in southern England. The GWCT biologists intensively culled predators in some parts of the study site but left them alone on others. The results of the study were striking, showing that the autumn partridge density was three-and-a-half times greater on the ‘culled’ site than on the non-culled site after only three years. Unfortunately, what this study wasn’t able to show was which predator(s) was responsible – all predators were culled, not just foxes. With this in mind, the biologists started radio-tracking the partridges and, in doing so, found that foxes were responsible for most of the deaths resulting from predation. Interestingly, GWCT biologist Jonathan Reynolds, in his Fox Control in the Countryside special report, noted:

Even if foxes had eaten all the partridges present, partridges could never be more than a few percent of fox diet. Thus partridges were probably not very important to foxes, but foxes were very important for partridges.”

So, while reports of large ‘hauls’ of game being taken from the stomach of a single fox (such as a report from County Durham in north-east England of a gamekeeper opening up a fox he shot to find 13 recently devoured grouse chicks in its stomach) are rare, even relatively low occurrence in the diet can seemingly have significant consequences for the gamebird population. Moreover, given that foxes are only one of a collection of predators, their impact can be additive. In 2007, for example, David Baines and colleagues at the GWCT published data on the mortality of the Black grouse (Tetrao tetrix) -- a gamebird in serious decline in the UK -- in three areas of Britain: North Wales; Northern England and the Scottish Highlands. Baines and his co-workers found that foxes were a significant predator of the grouse, taking 33% of adult birds in North Wales and 48% in the Scottish Highlands – these may not look like massive percentages, but the biologists also found that raptors (i.e. birds of prey) were also significant predators and, together, they had a significant impact on the grouse population. In addition, there is some evidence to suggest that there are certain seasons when predation is more likely. One study found that about a quarter of the 'large birds' taken by foxes in an area of southern Sweden were pheasants (right); the bulk of these were taken during the cubbing season (i.e. when foxes had cubs to feed). Similarly, on their study site in Dorset, Jonathan Reynolds and Stephen Tapper found that 70% of their foxes' diets were medium-sized birds and mammals (300g-3.5kg) and most of these were taken between April and June (cubbing season).

Ultimately, there can be little doubt that controlling predators (including foxes) can increase the percentage of game surviving, although it should not be assumed that predators are the only sources of loss. Back in 1935, Adrian Middleton published his study of the factors controlling partridge numbers in Britain, as part of which he looked at clutch losses between 1911 and 1924. Middleton found that foxes were the most significant predator of the birds and their nests, but he also observed that almost as many nests were destroyed by careless farm hands (344) as were raided by foxes (347). This was obviously several decades ago and practices have improved significantly since then, but it illustrates that even apparently trivial factors -- such as a careless farmhand -- can have sizeable impacts on these populations. (Back to Menu)

Arctic Fox (Vulpes lagopus)Arctic Foxes and other Carnivores
For many years we have known that many subtle interactions take place between carnivores living in the same area. The result can be that one species displaces (i.e. reduces the number of, or forces out altogether) another – this is called competitive displacement or competitive exclusion, according to the extent of the impact. Essentially when two species are competing for the same resources (food, shelter, space, etc.), one is often better at it than the other; the result is often that the ‘winner’ stays and the ‘loser’ goes. Several such competitive interactions are known for Red foxes; in some cases the foxes are the winners and in others they lose.

In his 1986 book Running with the Fox, David Macdonald recounted trials where Red and Arctic foxes (Vulpes lagopus) were released from fur farms on to various islands, from the Aleutians to the Alexander Archipelago, and left to fend for themselves. It soon became apparent that the two species could not be kept on the same island as the Reds invariably usurped the Arctics and, in one instance, Macdonald described how a single male Red apparently killed all the Arctic foxes on one small island during 1886. Evidence from elsewhere suggests that Red foxes can suppress the recovery of Arctic fox populations and may even set the southern limit of geographical distribution for the species. In the early 1900s, for example, the Swedish Arctic fox population crashed in response to over-hunting and, despite legal protection in 1928, the population never recovered; it has been suggested that predation by Red foxes was the reason.

More recently, a team of Swedish biologists found that Red and Arctic foxes were sympatric (had overlapping ranges) during the winter, but allopatric (used separate ranges) in summer, when the latter moved to higher altitudes to breed – they suggest that Arctics may risk coming across a Red fox during the winter when searching for food, but cannot risk the danger during the summer when they have cubs. Indeed, in a recent (2011) paper to the journal Polar Biology, Lomonosov Moscow State University zoologist Anna Rodnikova and six colleagues described the takeover of an Arctic fox breeding den along Russia’s Erkutayakha River by a Red fox in 2007. The Red fox approached the den and lay down, while the Arctic vixen sat at the entrance barking; eventually the Red fox moved closer, forcing the vixen to abandon her cubs and move away from the den. There was no indication that the Red fox, which appeared in poor condition, killed the Arctic cubs (the authors believe that the cubs hid in one of the chambers until an opportunity presented itself for escape). The Arctic vixen made no attempt to fight the intruder. While there are reports of both species co-existing together, there are also accounts of Reds actively attacking and killing Arctics. In a short paper to the journal Arctic in 2006, Nathan Pamperin and co-workers described the killing of an Arctic fox by a Red fox on northern Alaska's Prudhoe Bay Oilfield during November 2004. The video footage showed a Red fox chasing an Arctic fox, the two briefly fought and then the Red bit the neck of the Arctic and shook it violently; it then carried the body off to an undisturbed site and began biting at the back of the neck (around the shoulders), apparently trying to open the carcass. Over the subsequent days, it appears that the fox (or other foxes) partially consumed the carcass. Recently, scientists have raised concerns that the range expansion of Red foxes into southern parts of the Arctic tundra could lead to a reduction in Arctic fox populations.

It's not only Arctic foxes that Red foxes seem able to suppress the numbers of. In a 1995 paper to the journal Annales Zoologici Fennici, Swedish biologist Erik Lindström presented evidence that foxes could be a significant predator of Pine martens (Martes martes) and that high fox numbers can cause declines in Pine marten abundance. More recently another Swedish team, led by biologist Nils Carlsson, found evidence that, in areas of Sweden where fox populations had crashed following a mange epidemic, American mink (Mustela vison) populations had increased. In their 2010 paper to Biological Invasions, the authors noted:

"We suggest that the mink's population tripling was caused by a drastic decline in red fox populations, which caused terrestrial prey to increase. Later recovery of the fox populations reversed the trend and caused the mink population's recent decline."

In other words, the foxes weren't actively predating the mink -- as Lindström found with Pine martens -- but rather they were competitively excluding them. When the foxes died off, the mink had access to the foxes' food supply and their population increased.   Similarly, in a 2001 paper to the journal Oikos, a team of Swedish biologists led by Tarja Oksanen at Umeå University discussed the population regulation and cycling of carnivores and herbivores in the Northern Hemisphere. Oksanen and her colleagues suggested that winters with little snow cover may improve the hunting efficiency of generalist predators, such as the Red fox, at the expense of more specialist predators, such as the Least weasel (Mustela nivalis), and may consequently alter the population dynamics of the voles on which they both feed. For a more detailed exploration of how animal populations fluctuate (see Q/A).

Not all interactions with carnivores end in favour of the fox. It is widely known that large carnivores -- e.g. Eurasian lynx (Lynx lynx), Grey wolves (Canis lupus), coyotes (Canis latrans), etc. -- can displace foxes; in Britain even domestic dogs have been associated with deterring foxes from some urban areas. Coyotes and lynx seem especially intolerant of foxes and have been implicated in changes in their distribution and declines in their population in some regions (see Q/A). Recently it has been suggested that promoting the recolonisation of Australia by the dingo (Canis lupus dingo) could similarly serve to reduce or control Red fox populations there. Dingoes are large dogs native to Australia and there is evidence that they both target many of the same prey items that Red foxes hunt and, occasionally at least, kill foxes. In a paper to Global Ecology and Biogeography last year (2011), a team of Australian biologists led by Mike Letnic at the University of Western Sydney presented data on dingo and Red fox abundance in mainland Australia based on bounty schemes and field tracking. The data revealed consistently negative associations between abundance indices of these species – in other words, foxes appeared to be avoiding areas inhabited by dingoes. Indeed, foxes were most abundant in western New South Wales, where rabbits were plentiful and dingoes rare. It is suggested that dingoes could help reduce fox populations across Australia and thus offer potential relief to some of the continent’s native mammals that have declined since foxes were introduced.

European Badger (Meles meles)Closer to home, some studies have suggested that foxes may be displaced by European badgers (Meles meles - right). Observations of these two species in the field have long suggested that, when the two species meet, badgers are dominant to foxes, even though they may sometimes share setts or feed together in gardens. In 2004 the WildCRU team at Oxford University published some observations of badgers and foxes at artificial feeding sites at Wytham Woods. The results showed that the badgers were clearly dominant over foxes, fed in longer bouts and were less vigilant while feeding than foxes. Indeed, writing in their paper to the Journal of Zoology, the biologists explained:

Aggression between badgers and foxes was exclusively in the form of a badger charging towards a fox and swiftly displacing it. No instance of physical contact or injury was observed, and foxes never charged badgers.”

Foxes were, it seems, significantly more vigilant than badgers at feeding sites and the duration of their vigilance was associated with the number of badgers present (i.e. the more badgers around, the longer the fox was alert for). When the foxes arrived at the feeding site they would either choose an unoccupied feeder or wait for the badger to leave, while badgers commonly walked up and kicked foxes off feeders. The badgers rarely tried to chase each other away from a feeder: it appears a badger is less intimidated by another badger than a fox is! While foxes bolted when charged by a badger, in the absence of animosity neither species seemed perturbed by the other and foxes were often seen in the presence of badgers; the authors suggest that foxes may follow badgers to good feeding grounds. Indeed, the fact that foxes and badgers feed on many of the same prey items is probably part of the reason why fox populations appear to increase in the absence of badgers, as implied by data collected during the Randomised Badger Culling Trial (RBCT) in England between 2000 and 2006. During this time, badger numbers were reduced in a bid to assess what impact this would have on the incidence of bovine tuberculosis outbreaks in cattle herds. Upon analysing some of the RBCT data, a team of biologists led by Iain Trewby at the Central Science Laboratory in York found that, where badgers were successfully culled, average fox densities increased by about two-fold over those areas where badgers weren’t culled. Writing in the journal Biology Letters during 2008, Trewby and his colleagues suggest that killing badgers led to more food being available to foxes and thus their populations were able to increase – this is known as competitive release, or sometimes mesopredator release. It is important to recognise that this is only one study based around a comparatively small data set, but it provides some interesting food for thought and warrants further study.

Finally, it seems that foxes may not always give way to badgers at a feeding site and there is at least one report of a fox harassing an American badger (Taxidea taxus) for access to a carcass. In a paper to the Journal of Mammalogy during 1963 Minnesota-based biologist Edmund Hibbard described how a fox repeatedly lured the badger away from a sheep carcass. The fox would approach the feeding badger, which would break away to chase the encroaching fox. The fox, being the faster of the two, was able to run around behind the badger and arrive back at the carcass in time to take a few mouthfuls before the slower badger came back. Hibbard wrote:

It worked only because the nimble fox apparently “knew” that he could only entice the badger away by staying just barely out of the badger’s reach.” (Back to Menu)

Roe deer (Capreolus capreolus) kidDeer
While adult deer are generally outside the prey size range of Red foxes, dietary studies do occasionally find their remains in fox scat and stomach contents. Invariably most of these remains originate from carcasses that a fox has stumbled across (in some northern habitats such carcasses can be an important component of the fox’s winter diet), but in some cases the remains may be of yearling deer (called a calf, fawn or kid, depending upon the species). How significant foxes are as a predator of deer calves is unknown for most species, but their relationship with Roe deer (Capreolus capreolus) has been well studied.

In 1972, Helmuth Strandgaard presented data on a population of Roe deer at Kalø in Denmark; the data show that, when fox control in the area ceased, the number of Roe deer kids surviving dropped by 60%. Similarly, during a two-year study of Roe deer mortality in Sweden, Ronny Aanes and Reidar Andersen found that fox predation was the biggest cause of kid death. More recently, in 2004, Swedish University of Agricultural Sciences biologist Anders Jarnemo completed his doctoral thesis on neonatal mortality in Roe deer – i.e. how many, and by what means, new-born Roe deer kids died. Using data collected in two areas of central Sweden between 1986 and 2003, Jarnemo found that about half of the Roe kids died during the summer months and foxes were responsible for the majority (88%) of the deaths. The kids were most vulnerable to foxes during their first week of life, the threat decreasing with increasing age. Most (85%) kids were taken before they reached a month old, with only 2% of those taken being older than 40 days. In one of the areas, Jarnemo found that fox abundance was the only factor that had a significant impact on kid survival in any given year (i.e. more kids survived in years when fox abundance was low, such as during a serious outbreak of mange) and, in both areas, those born early or late in the season were most at risk from fox predation. Jarnemo also found that does (females) were more likely to lose a kid left hiding in open habitats -- where they were presumably more visible to foxes -- although they were quite capable of chasing away a fox if they spotted it.

Overall, it seems that foxes can have a significant impact on Roe deer kid survival, although how significant this effect is depends on various factors including the habitat in which the kid is hiding, whether the kid was born early or late in the season, how diligent the mother is, and presumably the availability of alternative food supplies (predation is likely to be greater in years when vole numbers are low).

One final point on the interaction between deer and foxes: not all encounters are aggressive or predatory. In May 2008 a gentleman posted on a wildlife Internet message board describing footage that he had been sent by a friend showing a fox and Reeves' muntjac deer (Muntiacus reevesi) in the garden of their London home. He explained:

“[the footage] is of an adult fox and a muntjac deer playing wildly together in the garden. They take it in turns to chase each other around the various shrubs etc. The fox looks the most enthusiastic of the two, cavorting and leaping around like a big kitten with those characteristic 'mouse jumps'.”

One forum member responded to say:

It's been seen before at Thames Valley Park by their night security officers, but so rarely you'd have to be very, very lucky to catch it on film”.

I would be very interested to hear from readers who have witnessed any similar behaviour. (Back to Menu)

Native Animals in Australia
Bearded DragonSince its introduction to Australia during the mid-1800s, the Red fox has been implicated in the decline of several native vertebrate species and considerable time, effort and funding have been diverted into trying to eradicate them from the continent. Foxes seem to have had the biggest impact on small to medium-sized birds and mammals (i.e. those in the 35g to 5.5kg range), and this predation seems to have severely limited both their abundance and distribution.

In 1975, Hans Brunner and colleagues of the Vermin and Noxious Weeds Destruction Board published their analysis of almost two thousand fox scats collected from a small forest in south-eastern Australia; they found that almost 70% of the diet was composed of mammals, particularly rabbits, rats, Pouched mice (Antechinus spp.), Ring-tailed possum (Pseudocheirus peregrinus), and the Bush-tailed possum (Trichosurus vulpecula). The remains of some other indigenous mammals -- e.g. Broad-toothed mice (Mastacomys fuscus), other possums and wallabies -- were also found, but these were uncommon.  Obviously, as we have already discussed (see: Food and Feeding), presence in the diet doesn't necessarily confirm predation – the meat could equally well have been scavenged. Nonetheless, there are data suggesting that where foxes are abundant, native mammals are rarer and fox predation in Australia is believed to have contributed to the decline of several native mammal species, including the Eastern Barred bandicoot (Perameles gunni), the Long-footed potroo (Potorous longipes), the Little penguin (Eudyptula minor) and the Bush-tailed Rock wallaby (Petrogale penicillata). It seems that foxes can have an impact on larger marsupial species too; with data suggesting that predation may also limit the populations of Australia’s Eastern Grey kangaroos (Macropus giganteus). Between 1993 and 1995 a team of biologists at the University of Sydney, headed up by Peter Banks, studied the impact of foxes on the kangaroo population in south-eastern Australia’s Namadgi National Park, finding that there were more juveniles in the population when fox numbers were controlled, than in areas where foxes were left alone. This dataset indicates that foxes were responsible for taking 25% to 35% of the juvenile kangaroos in their first year and, although not conclusive, suggests that foxes were limiting the population of this marsupial.

Some studies have suggested that foxes prey on native reptiles as well as mammals, and may thus detrimentally impact their populations too. A study conducted in Kichenga National Park in New South Wales (NSW) during the 1970s found the remains of Bearded dragons (Pogona vitticeps - above) in fox scats, although reptiles in general were rare. More recently, in a 2005 paper to Austral Ecology, Mats Olsson and his colleagues reported that fox removal increased the number of small, day-active lizards in open grassland habitats; they also observed a five-fold increase in the population of the Sand goanna (Varanus gouldii). Olsson and his co-workers concluded that removing foxes -- which compete with, and prey on, the goanna -- may allow the goanna to take over the role of top predator in the ecosystem.

Part of the problem for Australian conservationists is that foxes are not easy to control (see Q/A). A recent study in the Goonoo forests of NSW, for example, used camera traps to assess the impact of baiting (i.e. poisoning) on fox abundance. The biologists noted some impacts locally, but found that baiting had no effect on fox activity or abundance at the landscape scale; nor was there any clear effect on the populations of the prey species (i.e. there wasn’t increased activity or abundance of prey species where foxes were baited). Generally speaking, the impact of a baiting scheme is highly dependent upon the habitat and baiting strategy used. Indeed, an earlier study looking at the survival of malleefowl (Leipoa ocellata) -- a member of the partridge/pheasant family -- in the Yathong Nature Reserve, also in NSW, suggested that intensive and widespread baiting was necessary in order to reduce fox numbers sufficiently for this bird’s population to recover. There are many reasons why this is the case, including that foxes rapidly become bait-shy and dispersing individuals recolonise vacant areas rapidly, but it means biologists are faced with a daunting task.

Despite the foregoing, however, there have been some successes and a five year study (2001-2006) in the Eucalyptus forests of western Australia found that baiting foxes did have a significant impact on prey species in the area. In a recent paper to the journal Australian Forestry, Adrian Wayne and his colleagues reported that fox-baited areas had significantly more (in some cases, three-times more) individuals than un-baited areas, with the Bushtailed possum (T. vulpecula), wyolie (Bettongia penicillata), Southwestern Pygmy possum (Cercartetus concinnus), Western quoll (Dasyurus geoffroii), and the Shingleback skink (Tiliqua rugosa) being particularly abundant. It seems the areas regularly baited supported a greater number of species, as well as a higher abundance of individual species. (Back to Menu)

Black Slug (Arion ater)Plants and Invertebrates
Foxes don't just interact with other animals; they can also have an impact on the various plants with which they share their territory. While plant material (particularly fruit) is eaten by foxes, their influence extends far beyond this. The construction of fox earths (dens) and their activity in the vicinity alter the plant communities – plants are buried, trampled, destroyed by playing cubs, while fox scat and decaying prey remains act as fertiliser, changing the chemistry of the soil and promoting the growth of some species. Generally, the plant community is richer (i.e. has more species) in the vicinity of fox earths than in surrounding undisturbed land. In addition, the fox’s penchant for fruit may help plants spread and colonise new areas by dispersing the seeds in their scat: a process known as endozoochory. In a paper to the journal Restoration Ecology during 2010, Luis Matias and colleagues at the Universidad de Granada in Spain found that foxes living in south-east Spain's Sierra Nevada National Park were efficient seed dispersers for a wide range of woody plant species. The seeds of the Elmleaf blackberry (Rubus ulmifolius) and Hardy fig (Ficus carica) were most commonly found in fox scats and, in total, Matias and his team recovered almost 11 thousand seeds from 137 fox scats that they collected over three years; neither the Pine marten or Wild boar (Sus scrofa) had more seeds in their scats.

Finally, there is one other species that foxes may help spread that warrants a mention: the humble slug. In a fascinating 1987 paper to the Journal of Conchology, the late mollusc biologist Stella Davies suggested that, in urban areas, foxes may be an important means of transport for certain slug species – the slimy travellers hitching a ride on their fur coats. Davies notes that slugs have been found attached to the tails of domestic cats and are probably capable of latching on to the fur of most mammals allowing them to be carried to new locations. In this case, she was referring specifically to the Portuguese slug (Arion lusitanicus) in Britain, and noted:


Presumably many slugs as well as small insects and parasites could also find new habitats in a similar way. (Back to Menu)

Questions and Answers:

Are American and European foxes different species? = New!
Are British and European foxes different species? = New!
Are fox numbers increasing in Britain?
Are foxes colour-blind?
Are foxes getting bolder and, if so, why?
Are foxes native to Britain?
Are urban foxes getting bigger? = New!
Are urban foxes unique to Britain?
Can captive-bred or rehabilitated foxes be released back into the wild? [In Preparation]
Do foxes and badgers bury their dead?
Do foxes kill for "fun" and is surplus killing a waste?
How can I keep foxes out of my garden and secure my pets?
How significant are foxes and badgers as predators of hedgehogs?
Is it likely that a fox will attack me, my child, my cat or my dog?
Is it okay for me to feed wildlife? Am I causing any harm by putting out table scraps or seed for local animals?
Is there an exception to the fox scatter cache 'rule' and, if so, what are the benefits of scatter caching?
I've rescued an injured fox and want to keep it as a pet. Is that legal?
Should we be culling foxes in urban areas?
Should we reintroduce large predators to control the Red fox population?
What are Samson foxes? = New!
What do you know about losing a pet to a fox?
What is mange?
What is rabies and where does the fox fit in?
What parasites and diseases do Red foxes carry? = New!
What triggers dispersal in foxes? [In Preparation]
When and how did foxes come to live in our towns and cities?
Why are foxes so noisy? [In Preparation]
Why are foxes so smelly? [In Preparation]
Why do foxes kill their own young and the young of other foxes?
Why does my pet dog seem to have a penchant for rolling in fox poo?
Why extend your territory during winter?
Why help your parents raise your brothers and sisters?
Why shouldn't I feed animals chocolate?

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