Sunday, 15 September 2013

Caprines: The World's Largest Goats

Takin (Sichuan subspecies)
All of the various kinds of caprine that I have described so far in this series have looked, more or less, either goat-like or sheep-like. There are just two species left, and those form something of an exception. While most caprines are fairly medium-sized as hoofed animals go, these are much larger, more muscular, animals.

It used to be thought, on this basis, that they were closely related to one another, representing an early branch in the evolution of goat-like animals that split away from their relatives well before the appearance of actual goats or sheep. From modern genetic evidence, that no longer looks the case. They are, as we suspected, caprines, (although, despite the title of this post, not literally goats) but within that group, they are not particular closely related to one another. Instead, their apparent similarities are a coincidence, a case of parallel evolution where two animals, both fairly goat-like to start with, faced selective pressures to become larger.

The first of these animals is the takin (Budorcas taxicolor). Takins are very distinctive animals, quite hard to mistake for anything else, once you get a good look at them. The most obvious point, as I've already implied, is the size. A fully grown male takin stands over four feet high at the shoulder, and weighs upwards of 300 kg (660 lbs). The females are noticeably smaller, but still larger than even the males of any other caprine species (with, of course, one exception that I'll get to in a moment).

There seems to be some debate as to whether they're closer to goats or to sheep, although most of the evidence I've been able to find favours the former. Chances are they're probably descended from an animal that lived around the time of the goat-sheep split when such dividing lines weren't yet so clear as they are now. There are four subspecies, at least two of them with distinctive coat colours, and there has been some argument that they might be considered separate species. In general, though, unlike with some other caprine groups, this proposal has not been widely accepted.

The muscular bulk of takins goes a long way to making them look so different from other animals, and agile, mountain-climbing goats in particular. But there's also those short, backward-curving horns, the shaggy coat that almost (but not quite) includes a goat-like beard, and, of course, the colour. Depending on the subspecies, takins can be anything from a rich golden-yellow with a white snout, to dark brown with a black snout, while one subspecies has a mixed brown and gold pattern.

While their size means that they aren't as able to climb cliffs as animals like chamois or mountain goats, they do, nonetheless, live at high elevations, and often on quite steep slopes. They are found in and around the eastern Himalayas, and into some of the more mountainous parts of central China - the truly golden subspecies, for instance, is found only in the Qin Mountains.

Takins are primarily forest dwelling animals, inhabiting both broadleaf and coniferous woodlands on mountainous slopes between about 1200 and 3500 metres (4000 to 11,500 feet) - quite high by the standards of most animals, although rather lower than many other caprines in the Himalayas. Especially in the summer, they can also be found at or beyond the tree-line, migrating up-slope as the weather warms, to feed on high, treeless meadows. They're apparently determined enough to complete this migration that even a powerful earthquake isn't enough to put them off doing it on schedule.

For the rest of the year, though, they are found in more obviously lush environments, often with heavy bamboo undergrowth. Although, like many caprines, they'll eat pretty much anything, they are mostly browsers, feeding on leaves and herbs. Where the small size of animals like gorals allows them to selectively pick the choicest leaves, takins have the strength to rip down entire branches, rapidly stripping them bare of foliage and twigs.

Mostly active in the early morning and late afternoon, takins live in herds consisting of females, sexually immature males, and a few older males that dominate the breeding. For the several years during which they're old enough to mate, but not strong enough to have any chance of actually doing so, the males travel alone or in much smaller groups.

For the rest, however, the herds are not permanent assemblages. During the late summer breeding season, they break up into smaller groups, of about twelve to thirty or so individuals. This is a somewhat earlier rut than in many similar animals, perhaps partly because of their longer, seven-month, pregnancy, but also because the males apparently don't have to spend quite so much effort at that time of year looking for food, leaving more time for you-know-what.

They give birth to their single calf, therefore, in the spring. At this time, the smaller herds of the previous year gather together again, producing huge groups of a hundred or more individuals. This, it seems, is largely for defensive purposes, and its notable that pregnant takins don't wander off to some secluded location to give birth (as many such animals do), but instead stay with the herd all the time, everyone ganging up to protect the young calves.

Large though takins are, though, they are not the biggest of all caprines. That honour goes instead to the muskox (Ovibos moschatus). So stocky and heavily built is the muskox, in fact, that many people probably think of it as a bovine, like yaks, buffalo, or bison. However, it is genuinely a caprine, closer to goats than to cattle. In fact, the first part of its scientific name actually means "sheep-cow". Within the group, however, it seems to be more closely related to serows and gorals than it is to true goats or sheep.

Which is perhaps, surprising, since not only are those relatively small caprines, but they are the purest browsers within their group, while the muskox is the purest grazer. For that matter, they don't even live in the same part of the world. What's happened here is that, perhaps around 3 million years or so ago, one group of goral/serow-like animals came down out of the mountains and moved north, into Siberia. Caprines have always been good at surviving on marginal food in cold and barren landscapes, but the ancestors of muskoxen found that food, not on high mountain peaks, but in cold, northern plains. They did well during the Ice Ages, when such habitat was widespread, but, when the ice retreated, so did they.

At one point, then, muskoxen lived across Siberia, and into northern Europe. When sea levels were lower than they are now, a population even crossed the Bering land bridge and entered the Americas. Back home, they were driven to extinction, probably by late stone age hunters, but in their new American home, they survived, albeit with reduced genetic diversity compared to their forebears. For that matter, there used to be several different species of muskox, but only one now survives.

Today, those surviving muskoxen are native only to Canada and coastal Greenland. Most of Canada is just too warm for them to feel comfortable, so they keep to Nunavut and the Northwest Territories, with a great many of them living on the Arctic islands off the north coast, reaching as far as Ellesmere Island. These are lowland areas, quite different to the mountains most goats inhabit, and muskoxen obviously have no need of the cliff-climbing agility of their kin.

They are also staggeringly cold areas, with winter temperatures plunging as low as -40°C (which is also -40°F). It's because of this that that muskoxen have such thick shaggy coats - which make them look even larger than they are - as well as a thick layer of fat. They're actually not that much larger than takins, with fully grown males standing no more than five feet at the shoulder, and often rather less, but they can weigh up to 410 kg (900 lbs). Like takins, they have a sloping back, with shoulders noticeably higher than their rump.

Muskoxen are perhaps the greatest grazers of all the caprines, even more so than sheep, and they subsist primarily on grasses and sedges that they can dig out from under the snow. They'll certainly eat herbs and the like when they find them, but they inhabit such inhospitable, treeless, wastes, that really isn't much else besides grass that they can eat.

Studies of their digestive systems have shown that they chew the cud more thoroughly than animals with a naturally richer diet, such as moose, which presumably helps extract a greater quantity of nutrients from their low quality forage, at the expense of burning more energy to do so. In part, this is due to a "filter bed" effect, where food particles are retained for longer in the first chamber of the stomach, keeping them available for repeated regurgitation and chewing. Muskox calves have a channel that allows milk to bypass this process, ensuring that it doesn't over-ferment before they can digest it, but this disappears in adults.

Muskoxen live in herds of up to a dozen or so individuals in the summer, and up to thirty during the bitter cold of winter. When threatened, they gather into circles, with the strongest males facing towards the danger, and any calves safely protected inside the circle. This is an unusual, but very effective, defensive strategy. Intrestingly, a report from Liberec Zoo in the Czech Republic suggests that takins sometimes do the same thing, although this has yet to be observed in the wild. (In this case, the "threat" turned out to be muntjacs, but it took the takins a while to work out that the muntjacs were more frightened of them than vice versa).

They mate in the late summer to early autumn, and, for no particularly obvious reason, apparently prefer to do so at night. This is when the males get to use the musk for which they are named, secreting it from glands in front of their eyes, and rubbing it onto their bodies to attract females before head-butting their rivals until one of them gives in. They give birth to their calves eight months later - sometimes when the weather is still well below freezing.

Although humans proved successful at extirpating the native Asian and European muskoxen, the species has done well enough in Canada. The native population in Alaska was wiped out by hunters in the nineteenth century, but some herds from Greenland were transplanted there in 1936, and remain today, close to the north coast. (As with Canada, most of the rest of lowland Alaska is a bit too warm for the liking of muskoxen, and they aren't keen on mountains). Substantial populations have also been restored to northern Siberia, especially on the Taymyr Peninsula, and there are also a few now in central Norway.

[Photos by Trisha Shears from Wikimedia Commons, and the US Fish and Wildlife Service, in the public domain.]

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