Sunday, 27 April 2014

What Does the Otter Say?

Animals use a variety of different means to communicate with one another. For we humans, speech is the primary means of communication, but even we also have body language as a useful adjunct. (And writing, of course, although that's arguably just a representation of speech, and it's not, that we know of, something our species has always done). For other mammals, scent is usually at least as important.

The human sense of smell is pretty rubbish, by broader mammalian standards, but for those species where it functions effectively, scent can be an effective and useful means of communication. All you have to do is urinate on a lamppost or do what bears do in the woods, and you've left a long-lasting message that conveys all sorts of handy information to anyone who comes by later. But, on the other hand, it does have its limitations. In particular, it's not much good for rapid signalling, such as alarm calls. So, while we may be the only species to "speak" (in the sense of having complex syntactical rules), it's not surprising that we aren't the only ones to make vocalisations.

Having said that, unless you're a whale, vocal calls are really only useful for communicating with other animals that are at least in your general vicinity. As such, they're much less useful to animals that don't lead rich social lives. If you live all your life on your own, then it may be that the only sound you need to make is something to warn off intruders, and perhaps a little something for the breeding season. Apart from that, scent may well be sufficient to meet your needs.

Sunday, 20 April 2014

Mini-Monkeys: Madeiran Marmosets and More

Santarem marmoset
Back in the 1970s,  a survey of the monkeys of South America identified just two species of "typical" marmoset living in the Amazon jungle: a naked-eared form, and a tassel-eared form. Both species were fairly variable in appearance, and each was considered to include three distinct subspecies. Today, better knowledge of things like their genetic make-up means that we have elevated all of those subspecies to full species status.

The "tassel-eared marmoset" had first been described in 1811 by Geoffroy Saint-Hilaire (although the date is officially given as 1812, because it took a year to get the description published). Because it was the first to be so described, the other two were considered subspecies of it, rather than the other way round. Once they were split off, we were left only with the species to which the originally collected specimen belonged. While still sometimes called the "tassel-eared marmoset" or some variation thereof, it is now more commonly called the Santarem marmoset (Mico humeralifer) to distinguish it from its kin.

Sunday, 13 April 2014

Pleistocene (Pt 14): Ice Age Africa

Giant warthog
In the earlier parts of this series, when I described the animals of Ice Age Europe, I said that the continent, at that time, had a feel reminiscent of present-day Africa. But, if that's so, what was Africa like during the Ice Ages?

The answer is, perhaps disappointingly, "not that different to how it is now". Indeed, of all the settled continents, it's probably Africa that has changed the least since the Ice Ages. You might think that this has something to do with Africa being close to the equator; in particular, that it's too close for whopping great sheets of ice to have rolled across the countryside.

Which they didn't, so that much is true. Indeed, the southern hemisphere in general had far less ice cover than Europe, Asia, and North America. That's due mainly to the way that the continents happen to be arranged, with glacial ice sheets only being able to get as far as southern South America (there are fjords in places like Tierra del Fuego). Presumably, sea ice extended much further across the Southern Ocean than it does now, but that would have little effect on land-based animals.

But that's not to say that Africa, or Australia, were unaffected by the Ice Ages. Africa was colder than it is today, and, to begin with at least, rather drier, too. The Sahara and Kalahari deserts were more extensive than they are today, with the semi-desert belt of the Sahel being quite a way south of its present position, running through what are now fairly lush countries such as Guinea, Nigeria, and northern Kenya.

Sunday, 6 April 2014

Deep Dives to Dark Depths

There are something like ninety species of cetacean, which are usually grouped into fourteen families. Perhaps the most obscure and little known of these families - and among the most obscure of all mammal families - is that of the beaked whales. It's actually quite a large family, with over twenty species, representing almost a quarter of all known cetacean species, and around a half of all those that are noticeably larger than dolphin-sized. And, since they typically weigh a ton or more, they're hardly small themselves.

The main reason we know so little is where they live. These are deep-water animals, that rarely come in close to shore, and so just aren't seen very often. Combine this with the fact that they're mostly of little interest to whalers, and it becomes apparent that studying them is neither easy, nor likely to be commercially motivated.