Sunday, 21 July 2013

Caprines: Goats Among the Volcanoes

Japanese serow
While most goat-like animals today are grazers, subsisting on relatively large quantities of low-quality forage, it's thought that their ancestors were originally browsing animals, defending small patches of high quality food in otherwise inhospitable and craggy terrain. In the west, the most familiar surviving "resource defenders" of this kind are the chamois of Europe. While the exact evolutionary relationships of chamois aren't entirely clear, they are part of a broad cluster of species that is otherwise crammed with grazing animals, such as "true" goats and sheep.

Not so their counterparts in Asia, which form their own distinct evolutionary line, one that never appears to have given rise to true grazing animals. It is these species, not the chamois, that probably most resemble the ancestral goats from which all others evolved.

For much of the twentieth century, there were thought to be just three species that fit this description: two kinds of serow, and the goral. (It was also thought that the chamois were closely related to them, but we now know that that isn't the case). However, more recent research has shown that there are probably many more. In other words, what we thought were merely subspecies are almost certainly full species in their own right. I should add that this is by no means universally accepted, since it hinges a lot on how we define what a "species" is, but it is the most common view today, and therefore the one I will be using.

Serows were first described by Johann Bechstein in 1799, based on a population on the island of Sumatra in Indonesia. As the other species were separated off, it was therefore the Sumatran serow (Capricornis sumatrensis) that kept its original scientific name, even as the older name of "mainland serow" became increasingly inappropriate.

Despite the name, though, there are wild Sumatran serows on the Asian mainland, albeit in very small numbers; they can be found in peninsular Malaysia and the extreme south of Thailand. On Sumatra itself, they inhabit the Barisan Mountains, a volcanic range that runs the entire length of the island (and at twice the size of Britain, and larger than all but one of the contiguous US states, this is not a small island). Although more common on the lower slopes, they can be found as high as 3,000 metres (9,800 feet). This close to the equator, though, even the higher mountains are swathed in forest, and, with plenty of lush vegetation, it's apparent why the local serows never needed to evolve into more resilient, grazing animals.

Sumatran serow
Serows are thought to be mainly solitary, although females have been seen in small herds, of up to seven or so individuals. This sort of small group living is typical of "resource defenders", as well as making it easier for them to take shelter in dense vegetation. Serows are relatively large goats, standing about 90 cm (three feet) at the shoulder, and therefore larger than many ibex, let alone chamois. As might be expected in a tropical animal, their hair is short, although do have a mane of long white hair on their shoulders that contrasts with the sheer black of the rest of their bodies. Their horns are short and slightly curved, 28 cm (11 inches) at the very most, and even shorter in females.

They mate at the beginning of the rainy season, in October to November, giving birth to a single kid seven months later, just as the dry season begins (not that there's much difference between the two on Sumatra). They aren't present in very high numbers, with the Malaysian and Thai populations especially small, and were considered an Endangered species until just five years ago. While it turns out that they are more numerous than we previously thought, their population is still in decline, and there is a real risk that will be moved back into Endangered status before too long.

The most widespread of the serows is the Chinese serow (Capricornis milneedwardsii), which is found in much of southern China, and through Indochina as far south as southern Thailand. The more southerly animals are considered to belong to a separate subspecies to their Chinese kin, and may even be a full species, depending on how strictly one wants to draw the lines. Both forms can be distinguished from the Sumatran species by having reddish-brown legs, clearer white markings on their chin, and a more visible and dramatic shoulder-mane. Like other serows, they also have large scent glands immediately in front of their eyes, which are most likely used to mark their territories.

Chinese serows are sometimes found in lowland areas with dense forest and rugged limestone cliffs, but are more common in dense evergreen forests above 1,500 metres (4,900 feet). They have, however, also been found on some small offshore islands, and have even been spotted swimming between them.

We know rather less about the red serow (Capricornis rubidus), which is only found in the mountains of northern, and possibly western, Myanmar. They are distinctive enough in appearance, with reddish brown hair and no obvious mane, although it's not clear whether than might not also be true of some individuals of neighbouring species.

There are also reports of red coloured serows from Assam in India, but it's thought that these are actually reddish Himalayan serows (Capricornis thar), although they may conceivably be an as yet unknown subspecies, or even a new species.

Himalayan serows live along the entire length of the mountain range, from Myanmar to Kashmir, although they are most common in Nepal and Bhutan. They live at higher elevations than other mainland serows, up to at least 3,500 metres (11,500 feet). Although, they, too, live among dense vegetation, there are no tropical rainforests here as there are in Sumatra, and their range includes both broadleaf and coniferous woodlands, as well as heavy thickets of bamboo. They are known to favour steep slopes, with inaccessible forested gorges likely to be a particular favourite.

If these are the least known of the serows, the best studied by far is the one that has always been known to belong to a distinct species: the Japanese serow (Capricornis crispus). Smaller than most other serows, this stands no more than 78 cm (2' 7") at the shoulder, with males and females difficult to distinguish. They have a thick coat of fluffy grey hair, and short, pointed horns up to 15 cm (6 inches) in length.

Japan is a mountainous place, and, even though they avoid the heavily cultivated lowlands, there are still plenty of places for the native serows to live. While most common on Honshu, they are also found on the other main Japanese islands of Kyushu and Shikoku, although not in the northerly wilderness of Hokkaido. They live on vegetated mountainsides, with around two-thirds of their diet consisting of the leaves of deciduous trees, although that doubtless changes somewhat with the seasons, and they are also found, for example, among bamboo thickets and on high grassy meadows.

Japanese serows are often solitary, but, even aside from mothers with kids, they often live in mated pairs or family groups of three or four. Unlike most other caprines, they appear to be monogamous, presumably with the father at least helping with the child rearing (which is the main advantage of monogamy, biologically speaking).

Formosan serow
Young tend to stay with their mothers for about a year, although daughters can get away with it for longer than sons, before being driven off to find their own homes. This seems to be more to do with the fact that they don't like sharing food than, for example, because they need to avoid accidentally breeding with their parents or siblings. Once they find a territory, in true "resource defender" style they protect it from outsiders (other, of course, than their eventual mate), marking it with scent glands, or simply standing about on some prominent bit of rock and being obvious.

Most manage to find a mate somewhere between their third and fifth year, and breeding takes place in the autumn, with the single kid being born seven months later. They can live for up to fifteen years in captivity, although most don't manage more than half this in the wild.

Usually thought to be closely related to the Japanese serow, the Formosan serow (Capricornis swinhoei) is even smaller, has short reddish hair, and, uniquely for serows, no mane. It is found only in the mountainous eastern regions of the island of Formosa, or Taiwan; it was once more common in the lowlands, but has been driven back by human agriculture. It lives at surprisingly high altitudes, sometimes well above the treeline at up to 4,000 metres (13,000 feet). As this might indicate, they are closer to grazing animals than any of their kin, although they do prefer the lifestyle of a browser where they get the choice. Like the Japanese species, they are active throughout the day, whereas the mainland kinds of serow are more typically crepuscular, active around dawn and dusk and sheltering through the hottest parts of the day.

[Pictures by "ヤン提督", Mahbob Yusof, and "Peellden", from Wikimedia Commons. Cladogram adapted from Yang et al 2013 and Fernandez & Vrba, 2005].

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