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. (It is not, however, 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.

Sunday, 7 June 2015

The Dog Family: Foxes of Asia

Blanford's fox
Asia is a large and varied continent, home to no less than seven species of fox, even using the most narrow of definitions for that term. Three of these are also widespread on other continents - the red foxes of Japan, for instance, belong to the same species as those found in Britain and North America. Of the four that are (mostly) confined to Asia, I have already covered the corsac fox of the central steppe lands, but three still remain.

Heading east from Europe the first such species we come to is Blanford's fox (Vulpes cana). This is named for William Thomas Blanford, who first described it as a unique species in 1877 while working for the Geological Survey of India. Blanford, who discovered the animal in what is now Pakistan, seems to have been somewhat surprised that he was first European naturalist to notice it. He may have had a point, since it's fairly distinctive.

Sunday, 31 May 2015

Pliocene (Pt 5): The Last Sabretooths in Europe

Homotherium
Apologies for the absence of a post last week. This was due to personal circumstances that meant I just couldn't bring myself to write. Normal service has now been resumed.

Six million years ago, there were many different kinds of sabretooth cat in Europe. That, however, all came to an end with the Zanclean Flood and the dawn of the Pliocene epoch. It's not that they literally drowned in the flood, of course - almost by definition, most of the parts of Europe we know today were above where the flood waters stopped. But Europe changed in the aftermath of the flood, seeing, over an admittedly long period of time to human eyes, a change in the nature of the herbivores that lived there. And, when the herbivores change, so do the animals that have to eat them.

Most of the European sabretooths died out in the very earliest part of the Pliocene. The one exception was the "terror cat" Dinofelis, which became perhaps the dominant large predator in Europe for the next million years or so. However, once the climate took a turn for the worse, and the long prelude to the Ice Ages began around three million years ago, Dinofelis followed its relatives into extinction.

Sunday, 17 May 2015

Knowing Your Children

Mother mammals raise their young until they reach independence. This is hardly a surprising statement, and, while mammals are by no means unique in this regard, it is one of their distinguishing features.

The mother may, of course, receive assistance in this sometimes arduous task. In monogamous species, the father also helps in raising his young, and this is one of the main reasons for evolving monogamy in the first place - if the young require care by two parents in order to stand a decent chance of survival, then the father had really better stay around. But this is not the only source of such assistance. In many mammals that live in social groups, we see the phenomenon of alloparenting. This means that individuals other than the parents take up some of the burden of looking after the young. Usually these are younger, non-breeding, females, cooperating to raise infants communally, although it doesn't have to be.

At least 120 mammal species, and an even greater number of birds, engage in this to at least some extent. The benefit to the infants is obvious, especially where they require a significant investment in time and effort in order to reach maturity. But what's in it for the alloparent?

Sunday, 10 May 2015

Spot the Difference

Common European shrew
The shrew family contains what are, by the usual method of measuring such things, the smallest of all living mammals. Yet they are actually quite a large group, with well over 300 species so far identified, and, given their small size, probably quite a lot that we don't yet know about - especially in the tropics. Indeed, in the grand list of mammal families, they come fourth in terms of sheer number of species, beaten only by the rats and mice, the cricetids (most, of which, frankly, are also mice, although the group also includes the voles and hamsters), and the vesper bats. They may not have the greatest range of physical variation, at least to human eyes, but that's still quite a lot of diversity, and they certainly aren't "all the same".

It's perhaps worth pointing out, though, what a shrew is, and what it isn't. Firstly, while they may look kind of like mice, shrews are not rodents. Rodents are defined by the presence of great gnawing incisor teeth, and by not having the second set of incisors that rabbits have. Shrews don't look even remotely like this, having lots of small sharp teeth ideally suited for biting into insects. In fact, shrews' closest relatives are actually the moles and hedgehogs - relatively small animals that also eat a lot of invertebrates.