Sunday, 20 July 2014

Learning To Be a Good Mother (If You're a Squirrel)

Like birds, but unlike many other kinds of animal, mammals spend a lot of time raising and protecting their young. It's therefore obviously important that mother mammals have some kind of instinctive understanding of what to do to look after their children. And instinct does, indeed, play a big role in maternal care - even among humans, we talk about a mother's "instinctive" desire to protect and nurture her children.

Among humans, though, it isn't all instinct; we have many ways of learning even something as basic as this. But how true is this of other mammals? In fact, there is solid evidence that other animals get better with practice. Instinct may be important, but animals are capable of learning from experience, and a second-time mother generally has a better idea of what she's doing than one who's new to the whole thing. Indeed, not all wild animals are equally good mothers. There is strong evidence, for instance, that animals that suffered the equivalent of child abuse when young grow up to be poor parents themselves.

Sunday, 13 July 2014

Mini-Monkeys: Monkeys with Moustaches

Emperor tamarin (bearded subspecies)
Monkeys of the marmoset family, which include tamarins, are known, not just for their small size, but also their luxuriant fur, which often forms extravagant tufts on the head. Arguably, none of these tufts are more distinctive than the drooping moustaches of emperor tamarins (Saguinus imperator).

Emperor tamarins live in the lowland jungles just east of the Andes, in the border regions between western Peru, northern Bolivia, and eastern Brazil. Perhaps because of this remote location, they were discovered remarkably late for an animal so distinctive; they were first described by Brazilian zoologist Émil Goeldi in 1907 (and we'll be coming back to him in a later post). On the plus side, this distance from civilisation has kept them relatively secure, with loggers and the like only recently having reached this far into the jungle.

Compared with some other members of their family, they are not especially colourful. Their bodies are grey, reaching near-black on the face and hands, and they have a reddish tail with a grey tip. What makes them so noticeable, of course, are those long, pure white, moustaches, which are present in both sexes.  Indeed, the more widespread of the two subspecies also has a thin and straggly beard hanging from its chin. The moustache apparently reminded Goeldi of Kaiser Wilhelm II, although to be honest, it's hard to see why (one would have thought that some of the Chinese emperors would have made a better fit).

Sunday, 6 July 2014

First of the Fossil Dolphins

Hemisyntrechalus
The dolphin family is the largest family of aquatic mammals, by number of species. As I've mentioned a few times before, exactly how we're supposed to divide it up, and what scientific names we should give its various members is a matter of some debate. Genetic analyses designed to show which species are related to which just show a tangled mess. So, while we do know that the scheme we use at the present is wrong, we don't really know what we should replace it with, and, for the time being, we're stuck with what we've got.

The reason for this is likely a very rapid burst of evolutionary change, with numerous new species arising at more or less the same time. By examining the genetics of different species, and using what we know of mutation rates, we can make a guess as to when this happened. It turns out to be shortly before, or perhaps during the beginning of, the Ice Ages, in the late Pliocene to early Pleistocene. That at least one species seems to have arisen as a hybrid between two of the others - with the arms of the family tree effectively crossing back over again - doesn't really help matters.

Sunday, 29 June 2014

The Family Lives of Japanese Badgers

As I mentioned previously as part of my overview of the weasel family, we used to think that the "common", or Eurasian, badger inhabited much of that continent, with individuals found from Britain to Japan. We now know that that's not the case; there are at least three different species of badger within this area, albeit very closely related.

In Britain and Ireland, we think of badgers as living in communal setts, with multiple different family groups sharing the same network of tunnels and chambers, that may have built up over generations. Yet, while this is true in the British Isles, it isn't true anywhere else, even when we are looking at the exact same species where it lives on continental Europe. Here, as with most other members of the weasel family, European badgers live alone when they aren't raising their young.

The reason for this is thought to be a combination of Britain's climate and a diet rich in earthworms.The frequent rains in the British Isles are good for earthworms, and there are so many available to eat that the badger population in the islands is unusually high, something that they deal with by crowding together in larger groups. Elsewhere in Europe, there are less earthworms, and the badgers have a broader diet, but one that requires them to defend their territory from others of their own species if they don't want to starve.

Sunday, 22 June 2014

Fur Seals Going on a Winter Holiday

Once each year, animals like seals and sea lions haul themselves out of the water to spend time on rookeries located on remote coasts or distant islands. Once there, the females give birth to their young, raise them to the point that they can swim effectively, and then take part in the long orgy of reproduction during which the males fight for their affections. And then they all return to the water again, living out the rest of the year at sea.

For obvious reasons, nature documentaries tend to focus on this time of a seal's life. Scientists, too, know rather more about what the animals are up to when they're on land where they can see them, than they do about what they're up to when they're away from the coasts. Yet, fun though reproduction undoubtedly is, most of a seal's life is spent at sea, not at their annual breeding grounds. With modern tracking technology, however, we're beginning to get a better picture of what seals do during this time, and where they do it.

Take the northern fur seal (Callorhinus ursinus). Technically, these aren't seals, in the sense that they don't belong to the seal family, bur rather to the sea lion family. That's a bit confusing, so the term 'seal' is often used more broadly than that, and the two families are distinguished as 'earless seals' (the actual seal family, the Phocidae) and 'eared seals' (the sea lion family, including, of course, the sea lions themselves). That is, you can either consider sea lions to be a special kind of seal, or fur seals to be a special kind of sea lion. Or both, if you must. Take your pick.

Sunday, 15 June 2014

Mini-Monkeys: Chilling Out With the Mantled Tamarins

Golden-mantled tamarin
Over the last five months I have looked at the 22 widely recognised species of marmoset. However, as I mentioned back when I started, not all members of the marmoset family are actually marmosets. Almost all of the others are tamarins, the majority of which belong to the genus Saguinus, also known as the 'true' tamarins.

So what is the difference between a marmoset and a tamarin? On the face of it, they look quite similar, and, indeed, being members of the same family, that's not entirely inaccurate. They're roughly the same size, have the same luxuriant fur, often with extravagant tufts, and have the same basic body plan, with a long non-prehensile tail, clawed toes, and so on. The most significant difference though, and the one on which they were first separated back in the early 19th century, is in the shape of their teeth.

Unlike marmosets, tamarins have prominent canine teeth in their lower jaw. These are often called "tusks", although by a strict definition, tusks have to project outside the lips (as they do in wild boars or elephants), which these don't. In fact, they're actually no larger than those of marmosets, they just look that way because the incisor teeth that separate them at the front of the mouth are of a more normal size. In marmosets, the incisors are elongated and cylindrical, forming a straight line with the top of the canines, but in tamarins, the closer in size to what you'd expect in monkeys, making the canines stand out.

Saturday, 7 June 2014

Pleistocene (Pt 15): Ice Age Down Under

Procoptodon
The island continent of Australia has today what is probably the strangest mammalian fauna of any continent. Yet it is also the continent that has, perhaps, suffered the greatest number of mammalian extinctions over the last 50,000 years or so. Many of those are relatively recent, or at least after the end of the last Ice Age around 10,000 BC. But even compared with the Australia of, say, the 18th century, the wildlife of Ice Age Australia looked pretty odd.

In climactic terms, Australia didn't suffer too badly from the Ice Ages. It's too close to the equator to have had ice sheets get anywhere near it, although doubtless there was rather more snow on the mountains. (Although perhaps not too much - even today, Australia is the only continent to lack glaciers). Then, as today, much of the continent consisted of desert, and the bits that weren't were mostly arid grassland, albeit with denser woodlands around the eastern and northern coasts.