Sunday, 26 July 2015

Pliocene (Pt 6): Attack of the Hyenas

Pachycrocuta brevirostris
Pliocene Europe was a continent as yet untouched by human hand - although, as I've noted, not of non-human primates. One might think that, in the absence of humans, sabretooth cats were probably the thing that other animals had to fear the most. There's probably a lot of truth in that, but they were far from the only carnivores in Europe at the time, and some of them were pretty fearsome.

On the other hand, there were also much smaller carnivores, too. At the bottom of the scale, weasels, badgers, otters, and martens already existed on the continent, and may have been quite common in the forests of the time. Foxes also survived the Zanclean Flood, and have continued living in Europe, right through the Ice Ages, up to the present day. In fact, Pliocene foxes would have looked remarkably similar to those of today, and are generally placed within the same genus, Vulpes.

Similarly, the largest carnivores of the European Pliocene would also have looked familiar. These were the bears, dominated by the gianr Agriotherium, which may have been slightly larger than a modern polar bear. Another woodland creature, it had perhaps been more common in the previous epoch, but survived throughout almost the whole of the Pliocene, dying out not long before the Ice Ages began in earnest.

Sunday, 19 July 2015

Greeting Old Friends

There are two species of chimpanzee currently recognised. Until recently, the common chimpanzee (Pan troglodytes) was by far the better known of the two. Today, it's probably fair to say, though, that the other species, the pygmy chimpanzee or bonobo (Pan pansicus), is well-known enough that when people say "chimpanzee" they often mean "as opposed to a bonobo", rather than referring to both species collectively. For clarity, I'm going to use the more specific term of "common chimp" for P. troglodytes in this post.

At any rate, being very closely related, the two species have a lot in common. (Neither, incidentally, is closer to humans than the other, in much the same way that if your aunt has two children, neither of those children is more closely related to you than the other). But there are also striking differences, particularly in the way that they interact with one another socially. A recent study, for example, shows that bonobos make eye contact with one another more frequently than common chimps do with their own kind. This is the sort of finding we would expect for an animal where social cooperation and coordination are all-important; in contrast, common chimps are more likely to focus on the mouth, and on whatever object their fellow is currently interested in himself.

Sunday, 12 July 2015

Bats in the City

Common pipistrelle
Many mammal species change the environment around them to suit themselves, whether it be by digging burrows or building beaver dams. Yet none has had an effect even close to that of humanity. Sometimes we reclaim land from the sea, or flood valleys to make reservoirs, but we also chop down trees to make room for agricultural land, and divide natural habitats with roads and railways. Arguably the most dramatic alteration we make to the landscape, however, is the construction of urban areas - an entirely new kind of habitat, unknown on Earth before our arrival.

Urban areas, are not, of course, entirely devoid of animal life. Many animals wander into the peripheries, and sometimes even into the centres, of our towns and cities. A general term for such animals used to be synurbic, but, over the last few years, this term has become more precisely defined, not to mean just any wild animal that is happy to live in urban environments, but those that actually prefer to do so. That is, there are more of them per unit area in cities than there are in the wild.

Sunday, 5 July 2015

The Dog Family: Foxes of the American West

Swift fox (in summer coat)
There are six living species of fox native to the North American continent. One of those is the red fox, which is also found through much of Asia and Europe. Three others, including the grey fox of the southern US, are not traditionally considered to belong to the genus Vulpes, and I will be returning to these at a later date. Which leaves two close relatives of the red fox that are unique to the continent. Both, as it happens, live out in the wilds of the American West.

Heading out into the west, the first of these two species we come to is the swift fox (Vulpes velox). The native range of this animal happens to line pretty up well with a series of interstate borders, and it's found from northwestern Texas/eastern New Mexico in the south to western South Dakota/eastern Wyoming in the north.

As one might imagine, given this area, they like flat, wide open short grass prairie, and apparently avoid everything else, although they don't seem to have a great problem with cropland. They are small foxes, standing only about 30 cm (one foot) high, similar in height to a small terrier or a King Charles spaniel, although, due to a slim build, they are also considerably lighter than those dog breeds. During the winter, they have a dark grizzled grey back with tan markings on the flanks and legs, but, aside from the black tip to the tail and the pale belly, the whole animal takes on a browner hue in the summer, when it sheds its thick pelt.

Sunday, 28 June 2015

The Beardogs that Travelled the World

Amphicyon
Dogs and bears are two quite distinct families of carnivoran mammal, and nobody today is likely to mistake one for the other. They both belong to the same half of the carnivoran family tree, separate from the one that gave rise to such creatures as cats and mongooses. However, their half of the tree also included such animals as weasels, seals, and raccoons, so it is quite diverse. Furthermore, within that branch, bears and dogs are not particularly closely related, last having shared a common ancestor something like 50 million years ago.

However, before we get back that far in evolutionary history we discover that, for much of the Age of Mammals, there was an additional family of animals belonging to the broad group that includes both bears and dogs, and which is no longer with us. These were the beardogs, more technically known as amphicyonids.

Beardogs were not, despite the name, the ancestors of bears and dogs. They were a separate family, one containing animals that looked a bit like bears and a bit like dogs, and which needed a common name of their own. "Beardogs" gets across both those physical features and the fact that they are, indeed, related to the two living families... having said which, it is not at all clear which, if either, of the two they are closer to, in part because the first of them appeared so early.

Sunday, 21 June 2015

Seals, Sea Lions, and Finding Your Children

As I discussed just a few weeks ago, there are advantages to being able to identify your own children. It really does save the mother a lot of effort, especially when she can only look after a limited number of children at a time. As I pointed out then, mistakes do happen, and there are sometimes good reasons to look after other mothers' children, especially if the other mother happens to be your sister or something. But, generally speaking, getting the right child is a good idea.

Mother mammals can use three different methods to identify which child is their own, and likely often use a combination of them. Perhaps the most common method is smell, since most mammal species have a quite remarkable sense in this regard. If each child has a unique smell, or even if it just smells of you, that's a good way of identifying it. The other possibilities are identifying them by the sound of their voice, and, finally, by what they look like. For we primates, the latter may seem the most obvious, but facial recognition is something we're particularly good at.

Sunday, 14 June 2015

First, Find Your Marmot

Rodents are, on the whole, small animals, with mice, voles, and squirrels being among the most familiar examples. Yet, even within those families, much larger animals also exist. In the mouse family, of course, there are the rats, some of which are, indeed, rodents of unusual size. The largest of the squirrels, on the other hand, are the marmots.

Marmots, of course, are ground squirrels, not the tree-dwelling sort, and their closest relatives include animals like prairie dogs, along with assorted other species across the Northern Hemisphere. They are, for the most part, mountain-dwelling species, with the groundhog of Canada and the eastern US being a well-known exception. Groundhogs, like other North American species, and, for that matter, the Alpine marmot of Europe, are a well studied species, about which we know a fair bit. The various species found across Asia - and there are at least six - are generally less well-known.