Sunday, 22 May 2016

Bovines: Almost-Cows of Southeast Asia

Banteng female
So far, in my survey of the Bovinae subfamily, I've mostly looked at species that most Westerners are, if not personally familiar with, at least well aware of: domestic cattle, yak, and bison. The exception, perhaps, is the gaur, an unusually large (or, at least, tall) species of bovine native to Southeast Asia. The gaur, however, is not alone, for there are two other very closely related species that are native to the same general area.

The better known of these is likely the banteng (Bos javanicus), an animal that was once found from eastern India to southern China, and across the whole of the Southeast Asian peninsula; there are even distinct subspecies on Borneo and Java. Today, the wild animal is extinct in India and Bangladesh, and found only in a few limited patches elsewhere. It has been formally listed as an endangered species since 1996, but the species as a whole is in much better shape than that would suggest... because this is another species that has been successfully domesticated.

The domesticated animals are known as Bali cattle, and they are in wide use across Indonesia and Southeast Asia. Over the years, a number have escaped from captivity, with the result that at least some feral populations are now found on a number of Indonesian islands that did not (so far as we can tell) ever host the genuinely wild form. More dramatically, British troops took some of them to the Northern Territory of Australia in 1849, but released them all just one year later when crop failure forced them to abandon their new settlement. The resulting feral animals are still there, and, while there are several thousand of them, all in Garig Gunak Barlu National Park near Darwin, since they are descended from just 20 imported animals, it's perhaps unsurprising that they are now highly inbred.

Sunday, 15 May 2016

Toothless Old Fossils

Artwork depicting extinct animals almost invariably shows them physically fit, unless they're actively engaged in some life-or-death battle. They're usually either adults in the prime of life, or still juveniles (often newborn). And this is actually quite reasonable, since few animals get to live to an old age out in the wild. Most will, after all, be eaten before then, and if they have any serious illness or crippling injury, they're not going to last long. Senescence, the gradual decline of biological function associated with becoming elderly, is not something we see much in the wild, for all that it's common in humans and domestic animals.

Which isn't to say that we don't see it at all, especially in very large animals that have few, if any, natural predators once they reach adulthood. The same must also have been true in the distant past, and it's reasonable to assume that at least some fossils, at least of the larger animals, belong to elderly individuals. It isn't, however, necessarily going to be all that obvious, especially if the skeleton is incomplete in the first place. Nonetheless, a recent report does describe a jawbone that the authors believe belonged to an elderly animal, and, if they're right, this offers some unusual insights into the creature in question.

Sunday, 8 May 2016

Friends and Family Among the Degus

A great many mammals are solitary. They spend most of their adult lives more or less alone, only meeting up with others of their kind in order to mate. Apart from a mother with her young, the extent of their social lives outside the mating season is just driving off rivals. But, of course, there are a great many that are sociable amongst themselves, forming herds, packs, or other associations. For a herbivore this often provides safety in numbers, while a pack-hunting predator may have the ability to take down larger prey than it otherwise could.

How does social living get started, in evolutionary terms? Perhaps the simplest way is that children simply fail to leave their mother, creating a fairly permanent family group. According to one theory, such groups are likely to become particularly stable if there are not enough resources around (for whatever reason) to allow the children to wander off and have young of their own. In these situations, the theory proposes that the older children hang around in order to help their close kin, such as younger siblings, and thus have at least some chance of passing their genes on to the next generation.

Sunday, 1 May 2016

The Largest Weasel Ever?

The weasel family were the first group of mammals that I decided to spend a year describing in detail on this blog, back in 2011-12. I concluded the series with a look at their fossil history, stating, among other things, that the fossil genus Enhydrodion "may" have been the largest member of the family to have lived. This, however, relies on guesswork relating the size of the body of the animal to its skull, which is all we have in any completeness. But there are, in fact a number of other fossil members of the family with even larger skulls, so a lot rests on their exact bodily proportions, which are often a mystery.

Such examples include the giant wolverine Plesiogulo (for which we have not only the skull, but, just possibly, the penis bone), the giant hypercarnivorous honey badger Eomellivora, and the relatively long-legged Ekorus, whose relationship to other mustelids is unclear. But, according to a new analysis, the largest mustelid skull known belongs to an animal called Megalictis ferox.

Of course, calling Megalictis a "weasel" is a bit of a stretch. The weasel family is very diverse, including such animals as otters, badgers, and wolverines, as well as more obvious examples such as polecats and stoats. So, yes, it's really only a weasel in the same sense that a badger is... and that's assuming it's a member of the weasel family at all. So, let's start with that - what is this animal, and is it really a mustelid?

Sunday, 24 April 2016

Bovines: Bison bison bison, the Bison

American bison
The only bovine native to the Americas is the bison (Bison bison). Indeed, it is one of only five species of bovid that fit that description - the other four all being members of the goat subfamily. To give at least some variety, however, there are two generally recognised subspecies of American bison, one of which, following the standard rules for naming subspecies, necessarily goes by the wonderfully tautonymous trinomial Bison bison bison.

This, in fact, is the plains bison, which was once found across pretty much the whole of what is now the contiguous United States, leaving aside only the Pacific and Atlantic coasts and the arid deserts of the Southwest; they also lived in far northern Mexico and up as far as central Alberta. The other subspecies, commonly known as the wood bison (Bison bison athabascae) is native to north-western Canada and to Alaska. Physically, it's slightly larger than its southern relative, which means that, in the absence of American rhinos, elephants, and so on, it is, in fact, the largest living, land-dwelling animal of any kind native to the Americas.

Because bison are, indeed, pretty big. A fully grown male can be anything up to 195 cm (6' 6") tall at the shoulder, and can weigh as much as a tonne (2,200 lbs). Females are, admittedly, quite a bit smaller, although at a maximum of about 180 cm (6') and 550 kg (1,200 lbs) they're still pretty big - and closer in size to the males than, say, those of yak. The horns are also about the same size in both sexes, although (relative to the rest of the animal) fairly small in comparison to those of most other bovines.

Sunday, 17 April 2016

Pliocene (Pt 10): Before There Were Zebras

At the dawn of the Pliocene, Africa, like Europe, was a much wetter place than it is today. As a result, it was also much greener, a place of lusher vegetation, and the animals that fed on it. While that likely made little difference to the heart of the Congo jungle and to the more tropical reaches of West Africa, which are about as green as they're going to get, elsewhere the changes would have be obvious to any putative time traveller.

The biggest difference was likely in the north, where the even the very heart of what is now the Sahara Desert was likely covered in arid scrubland - hardly hospitable, but a significant improvement over baking hot dune-fields. By one estimate, moist savannah and open woodland stretched as far north as 21°, covering what are now countries like Chad, Sudan, and Mauritania. Further east, Somalia would also have been covered by woodland, rather than its current dry grasslands, and, at the opposite end of the continent, there may have been small forests in what are now the Namib Desert and the Kalahari.

It didn't last, of course. Around 3 million years ago, as the world fell irrevocably into the long autumn of the late Pliocene, Africa became not only cooler, but drier. And, if the generally cooler climate did not make too much difference to a continent sitting on the equator, the loss of rain certainly did. It's at this time that the Sahara, and the other deserts we are familiar with today, began to form, and the wildlife had to either adapt to that fact, or die. What was good news for voles in Europe, promoting the tougher grasses on which they thrive, was bad news further south, where the grass gave way to open sand.

Sunday, 10 April 2016

The Last Seals of the Mediterranean

There are eighteen recognised species of "true" seal (that is, as opposed to fur seals, which are actually more closely related to sea lions). Three of these species are currently listed as endangered under the most widely recognised international standard for such things, the IUCN Red List. Compared with some other groups of animals - rhinos being a particularly obvious example - this isn't really all that bad. But it could, of course, be rather better.

One of the endangered seal species is the Caspian seal, found only in the isolated and land-locked sea of the same name. The other two are monk seals, with one species each in the Mediterranean and off the coast of Hawaii. Quite how two such closely related species ended up on opposite sides of the globe is something I've discussed in an earlier post, but for today, the key point is that there used to be three species of monk seal, and that the other one went extinct around 1952.

Given this, the threat to the two remaining species is surely far from hypothetical. There are thought to be a little over a thousand Hawaiian monk seals alive today, but, as confirmed in a recent species review, the most endangered seal species of all is the Mediterranean monk seal (Monachus monachus) - the only seal species to live in the sea for which it is named.