The hoary marmot (Marmota caligata), the Alaska marmot (M. broweri), and the woodchuck (M. monax) are the three species of marmots that live in Alaska. The hoary marmot can be found at the bases of active talus slopes in the mountains of central, southeastern, and southwestern Alaska. It also occurs down to sea level along some areas of the coast. The Alaska marmot lives in similar talus habitat throughout much of the Brooks Range. The woodchuck digs its den in loess (wind-deposited soils) along river valleys in the dry lowlands of eastcentral Alaska.
General description: Large relatives of the squirrel, the hoary and closely related Alaska marmots weigh 10 pounds (4.5 kg) or more and may exceed 24 inches (61 cm) in total length. The woodchuck weighs between 2 and 6 pounds (.4-2.7 kg). They may grow to be 20 inches (50.8 cm) long. The animals attain their maximum weight in late summer, when they accumulate thick layers of fat that will sustain them through winter hibernation. Body shape is similar in all three species: head short and broad, legs short, ears small, body thickset, tail densely furred, and front paws clawed for digging burrows. Hoary and Alaska marmots are predominantly gray with a darker lower back and face and a dark, reddish tail. The hoary marmot has a white patch above its nose and usually has dark brown feet, giving it the Latin name caligata, meaning “booted.” The Alaska marmot does not have a white face patch, its feet may be light or dark, and its fur is much softer than the stiff fur of the hoary marmot. A uniform reddish brown, the woodchuck has an unmarked brown face. The name woodchuck originated as a Cree Indian word used to describe a number of similar-sized animals and does not describe characteristics of the woodchuck's behavior or habitat preference.
Life history: In Alaska, all marmots mate in April or May. About a month later, two to six young are born hairless and blind. The young disperse two months after birth and may breed for the first time when they are 2 or 3 years old. Marmots may live to 5 years or more. They feed on grasses, flowering plants, berries, roots, mosses, and lichens.
Hoary and Alaska marmots make their summer homes on the bases of active talus slopes, where the rocks protect them from predators and provide lookout stations. Woodchuck dens may be up to 30 feet long, are dug in the loamy soils of river valleys in Interior Alaska, and end with a chamber containing a large grass nest. Most marmot dens have a main entrance with a mound of dirt near the hole and a number of concealed entrances. Marmots are social animals. Although each family has a separate burrow, these burrows are located near each other, forming a colony.
True hibernators, marmots enter a state of torpor in winter during which all bodily functions are reduced. Hoary marmots and woodchucks hibernate alone in the same burrows in which they spent the summer. To protect themselves from the cold, they plug the tunnel leading to the nest chamber with a mixture of dirt, vegetation, and feces. They emerge from their winter hibernation in April or early May to find food and mates. Adapted to the harsher winter climate of the Brooks Range, Alaska marmots create a special winter den which has a single entrance and is characteristically located on an exposed ridge that becomes snow-free in early spring. The entrance is plugged after all colony members are inside, and no animals can leave until the plug thaws in early May. Consequently, Alaska marmots mate before they emerge from their winter den. These dens are relatively permanent for each colony, and some are used for more than 20 years. Because hibernation begins in September, most marmots in Alaska spend two-thirds of each year locked in their winter dens.
Marmots are most active in early morning and late afternoon, although they may leave their burrows during other daylight hours. Marmots need wind to control mosquito levels and rarely venture out on calm days. The Alaska marmot marks its territory by rubbing its face and glands on rocks and along trails. The hoary marmot probably marks its territory in the same way.
The pelt colors of marmots help them blend with the lichen-colored rocks or rusty-brown soil of their surroundings. Nevertheless, marmots remain alert for predators including eagles, foxes, coyotes, wolves, and bears. When the Alaska marmot is alarmed, it produces a slurred, low-pitched warning call. The alarm call of both hoary marmot and the woodchuck is a loud whistle. They also hiss, squeal, growl, and yip. In areas where marmots are hunted by humans, they have learned to remain quiet when humans approach. Good climbers and swimmers, woodchucks may also take to trees or water to avoid predators.
Marmots often secondarily benefit other animals and plants. Abandoned marmot holes can become homes for small mammals. In moderation, their digging and defecation loosen, aerate, and improve the soil. Alaska Natives have long relished marmot meat and used its thick coat for warm clothing. Although these wary animals are difficult to approach closely, persistent observers are rewarded by the fascinating sight of a marmot community.
The northern flying squirrel (Glaucomys sabrinus yukonensis) is a gliding (volplaning) mammal that is incapable of true flight like birds and bats. There are 25 subspecies across North America with Interior Alaska being the most northern and western limit of the species' range. The generic name, Glaucomys, is from the Greek glaukos (silver, gray) and mys (mouse). Sabrinus is derived from the latin word sabrina (river-nymph) and refers to the squirrel's habit of living near streams and rivers.
General description: Adult flying squirrels average 4.9 ounces (139 gm) in weight and 12 inches (30 cm) in total length. The tail is broad, flattened, and feather-like. A unique feature of the body is the lateral skin folds (patagia) on each side that stretch between front and hind legs and function as gliding membranes. This squirrel is nocturnal and has large eyes that are efficient on the darkest nights. Eye shine color is a distinctive reddish-orange. Flying squirrel pelage is silky and thick with the top of the body light brown to cinnamon, the sides grayish, and the belly whitish.
Habitat requirements: Flying squirrels require a forest mosaic that includes adequate denning and feeding areas. Den sites include tree cavities and witches' brooms. Tree cavities are most numerous in old forests where wood rot, frost cracking, woodpeckers, and carpenter ants have created or enlarged cavities. Witches' brooms, clumps of abnormal branches caused by tree rust diseases, are the most common denning sites of flying squirrels in Interior Alaska. About November or December, when temperatures begin to drop sharply, flying squirrels move out of cavities and into brooms. In the coldest periods of winter, they form aggregations of two or more individuals in the brooms and sleep in torpor.
Feeding areas preferred by flying squirrels contain fungi (mushrooms and truffles), berries, and tree lichens and may be in either young or old forests. Dried fungi cached in limbs by red squirrels are sometimes stolen by flying squirrels.
Flying squirrels probably get water from foods they eat and rain, dew, and snow. Constant sources of free water (lakes, ponds, and watercourses) do not appear to be a stringent habitat requirement.
In a year's time, a flying squirrel in Interior Alaska may use as many as 13 different den trees within 19.8 acres (8 ha). On a night foray, a squirrel may travel as far as 1.2 miles (2 km) in a circular route and be away from its den tree for up to 7 hours. It may change den trees at night and move to different ones more than 20 times over a year, staying in each for a varying numbers of days. Den trees with brooms are used more than twice as much as trees with cavities.
Fairly dense, old closed-canopy forests with logs and corridors of trees (especially conifers) that are spaced close enough to glide between are needed for cover from predators. High quality flying squirrel habitat can be a community mosaic of small stands of varying age classes in which there is a mix of tall conifers and hardwoods. Part of the mosaic must be old coniferous forest with den trees containing witches' brooms, woodpecker cavities, and natural cavities for nesting sites. Riparian zones provide excellent habitat in all coniferous forest associations.
Life history: Flying squirrels in Alaska may breed anytime from March to late June, depending on length and severity of the winter. The female can breed before 11 months of age and give birth at about 1 year of age. Gestation requires about 37 days, so the young are born from May to early July. One litter of two per year is probably the usual case for Alaska, but they are known to have litters ranging from one to six in other parts of their range. At birth, the young flying squirrel (nestling) is hairless, and its eyes and ears are closed. Development is slow in comparison with other mammals of similar size. Their eyes open at about 25 days, and they nurse for about 60 to 70 days. By day 240, the young are fully grown and cannot be distinguished from adults by body measurements and fur characteristics. Mortality rate for flying squirrels 1 and 2 years old is about 50 percent, and few live past 4 years of age. Complete population turnover can occur by the third year.
Individual flying squirrels nest in tree cavities, witches' brooms, and drays. In Interior Alaska, most brooms and cavity entrances have southerly exposures. Nests in cavities are usually located about 25 feet above the ground but may range between 5 and 45 feet. Flying squirrels excavate chambers in witches' brooms and line them with nesting materials. A dray nest is a ball-like mass of mosses, twigs, lichens, and leaves with shredded bark and lichens forming the lining of the chamber. Flying squirrels build drays entirely by themselves or modify the nests of other species (e.g., bird nests, red squirrel nests). The dray is usually positioned close to the trunk on a limb or whorl of branches with its entrance next to the trunk. Most drays in Alaska are probably conifers.
Food habits: The flying squirrel is omnivorous. While little is known about its diet in Alaska, the food it consumes in other parts of its range include mushrooms, truffles, lichens, fruits, green vegetation, nuts, seeds, tree buds, insects, and meat (fresh, dried, or rotted). Nestling birds and birds' eggs may also be eaten. Those observed foraging in the wild in Interior Alaska ate mushrooms (fresh and dried), truffles, berries, tree lichens, and the newly flushed growth tips on white spruce limbs. In spring, summer, and fall the diet is mostly fresh fungi. In winter it's mostly lichens. Flying squirrels are not known to cache fungi for winter in Alaska, but they are known to do so elsewhere in their range. Witches' brooms and tree cavities would be likely places to find their caches.
Predators and parasites: Owls, hawks, and carnivorous mammals prey on flying squirrels. Primary predators are probably the great horned owl, goshawk, and marten due to their common occurrence and widespread range in Alaska's forests. Three different flea species may infest a single squirrel.
Economic and ecological value: Flying squirrels are important to forest regeneration and timber production because they disperse spores of ectomycorrhizal fungi like truffles. Truffles are fruiting bodies of a special type of fungus that matures underground. They are dependent upon animals to smell them out, dig them up, consume them, and disperse their spores in fecal material where the animal travels. The animal serves to inoculate disturbed sites (e.g., clearcuts, burned areas) with mycorrhizae that join symbiotically with plant roots and enhance their ability to absorb nutrients and maintain health. The flying squirrel's ecological role in forest ecosystems, therefore, gives it economic value. In addition, they may be important prey for a variety of hawks, owls, small carnivores, and furbearers like marten, lynx, and red fox. Many Alaskans value flying squirrels just for their interesting habits and aesthetic qualities.
Management considerations: Logging for house logs, wood for fuel, and lumber can have devastating effects on flying squirrel populations if clearcut size is too large or if some scattered tall conifers in large cuts are not retained as cover and for travel across the open spaces. Management should include retention of other squirrel species in shared habitats. Snags with woodpecker holes or other natural cavities and coniferous trees with witches' brooms must also be maintained in managed forests in order to provide adequate habitat for flying squirrels.
The red squirrel (Tamiasciurus hudsonicus) makes itself quite conspicuous with its lively habits and noisy chatter. Cone cuttings on stumps or rocks are common and tracks in snow are numerous where this squirrel occurs. It can be found in spruce forests over most of Alaska and has a wide range in North America. It occupies a wide variety of forest habitat, occurring in the hardwood forests of eastern North America and the coniferous forests of the west and north.
General description: The active rodent averages 11 to 13 inches in length (28-33 cm), including tail, and is a rusty-olive color on the upper parts of its body with a whitish belly and underparts. In summer, a dark stripe on the side separates the upper rusty color from the white of the belly. The bushy tail is often a lighter orange or red with light tipped hairs.
Life history: Red squirrels are solitary but pair for mating in February and March. Females usually breed when they are 1 year old. Three to seven young are born after a gestation period of 36 to 40 days. The young are born blind and hairless, weighing about ¼ ounce at birth. They are weaned at about 5 weeks but remain with the female until almost adult size.
The young leave the female and are independent during their first winter. This means that they have to be successful at gathering and storing a winter's supply of food.
Behavior: Much of the red squirrel's time in the summer is spent cutting and storing green spruce cones. There may be several bushels of cones stored in a cache. Caches may attain a diameter of 15 to 18 feet and a depth of 3 feet. Red squirrels also cache mushrooms on tree branches. They eat seeds, berries, buds, fungi, and occasionally insects and birds' eggs. They are busy collecting and storing food from early morning until dusk and also on moonlit nights.
Nests may be a hole in a tree trunk or a tightly constructed mass of twigs, leaves, mosses, and lichens in the densest foliage of a tree (making the nest almost completely weatherproof). A loose mass of twigs and leafy debris in a high tree is used as a “fair weather” nest. Their ground burrows, also known as middens, are used mostly for food storage. There is usually one large active midden in each territory with perhaps an inactive or auxiliary midden.
The home range of red squirrels is about ½ to 1 acre, and each squirrel knows its territory well. Each squirrel has several nests in its territory and always seems to know which retreat is nearest. Territorial behavior seems to be most rigid during caching of food and relaxes somewhat in the spring.
The red squirrel is active all year but may remain in its nest during severe cold spells and inclement weather. They are agile climbers and, being extremely curious, will often attempt to enter buildings, upsetting anything they can move and gnawing on woodwork. Once in a house or cabin, they can be very destructive, tearing out insulation and mattress stuffing for use as nesting material and caching food stores in any available niche.
Predators: The main predators of red squirrels are hawks, owls, and marten. Other predators may occasionally take a squirrel but are not serious threats. Around populated areas, one of the predators is the domestic housecat.
Human use: The red squirrel is used to a limited extent by man for food and fur. Squirrels may be small but the meat is good eating. In parts of Canada and Alaska the pelts are sold for their fur. Red squirrels may damage trees, cutting off twigs by the bushel, but they are also helpful because they distribute and plant seeds of spruce and other trees.
The Arctic Ground Squirrel (Spermophilus Parryii) was named "tsik-tsik" by the Inupiat Eskimos on account of a call this little rodent makes when it is alarmed?
Tsik-tsiks are found in both arctic and alpine tundra. They fatten themselves on seeds, mushrooms and berries—almost doubling their body weight over the summer—in preparation for fall hibernation. Although they insulate their winter burrows with grasses and block the entrances with dirt, winter temperatures inside the burrows still fall well below 0° F.
During hibernation, the body temperature of the arctic ground squirrel drops from 98.6° F to 26.4° F—that's below the freezing point of water and is the lowest known body temperature of any living mammal. Most mammals, including people, would be frozen solid at that body temperature! Scientists aren't sure just how these diminutive rodents do it, but they apparently have developed a unique mechanism that allows their body fluids to become supercooled—to fall below the freezing point without crystallizing into ice and damaging cell tissue.
Periodically throughout the winter, the tsik-tsik will rouse itself, briefly raising its body temperature more than 70° F in four hours, before going back into hibernation. Not until late March or early April does the arctic ground squirrel finally emerge from its winter den to the light of another spring and six months of intense activity.
Arctic ground squirrels are the largest and most northern of the North American ground squirrels. This species is common in the ice-free mountainous regions of Denali. Permafrost and soil type are two of the most important factors limiting ground squirrel distribution in Denali.
Arctic ground squirrels are burrowing animals and they establish colonies in areas with well-drained soils and views of the surrounding landscape. Colonies often consist of multiple burrows and a maze of tunnels beneath the surface. Well-drained soils are important, as flooding of these burrows causes considerable problems for squirrels. Accordingly, squirrels usually avoid establishing colonies or excavating burrows where permafrost is close to the surface.
Like many other arctic animals, arctic ground squirrels have unique physiological adaptations that allow them to survive during winter. Arctic ground squirrels are obligate hibernators and spend 7 to 8 months in hibernation. Researchers at the University of Alaska at Fairbanks have shown that during hibernation, arctic ground squirrels adopt the lowest body temperature ever measured in a mammal. The body temperature of hibernating squirrels drops below freezing, a condition referred to as supercooling. At intervals of two to three weeks, still in a state of sleep, hibernating squirrels shiver and shake for 12 to 15 hours to create heat that warms them back to a normal body temperature of about 98 degrees Fahrenheit. When the shivering and shaking stops, body temperature drops back to the minimal temperature. This type of hibernation is rare among mammals and scientists are still studying this unique physiological behavior.
In Denali, ground squirrels are active from late April to early October, but the sexes and age-classes show some differences in their annual activity patterns. Adult males are usually the first to emerge from hibernation. They dig their way through the snow and stay relatively close to their burrows until the snow cover melts. Breeding occurs in May and a single litter of 5 to 10 pups is born in June. The young develop rapidly and usually emerge from their burrows in mid-July. By late summer, young abandon their natal burrow and occupy a neighboring, empty burrow or excavate a new one.
Adults start hibernating as soon as they have enough body fat to survive the winter, often in late August when plenty of foods are still available. It is probably safer to enter hibernation early, even when foods are accessible, than to remain on the surface vulnerable to predators. Youngsters, however, take much longer to find foods and put on body fat and they are often active until late September. This means that youngsters are more vulnerable to predation than adults.
The diet of arctic ground squirrels is diverse and opportunistic. They eat many types of vegetation including the leaves, seeds, fruits, stems, flowers, and roots of many species of grasses, forbs, and woody plants. They also eat mushrooms and meat from freshly killed animals (including ground squirrels). Because they are active only during the short subarctic summer, arctic ground squirrels must be efficient foragers. As summer progresses, they put on a tremendous amount of fat stores for the winter and often double their body weight by the time they enter hibernation in fall.
The social behavior of arctic ground squirrels is complex. This species is highly territorial and squirrels may kill other squirrels over territorial disputes. However, other related females in the colony often care for orphaned youngsters. Further, territorial behavior lessens during late summer, and male squirrels may move between colonies or establish colonies of their own.
So many different predators eat arctic ground squirrels that Adolph Murie called them the "staff of life" in Denali. They are one of the most important summer food sources for golden eagles, gyrfalcons, foxes, and grizzly bears.