Sunday 17 July 2016

Bovines: Mini-Buffaloes

Anoa (probably lowland species)
One of the themes that we see played out from time to time in evolution is that of insular dwarfism. Here, a population of some large animal is trapped on an island or (less commonly) some other isolated locale from which they cannot easily escape. Faced with a limited food and other resources, over sufficiently large periods of time, they become smaller, making the best of whatever there is. (There is also a related phenomenon of insular gigantism, whereby really small creatures become larger, likely because they no longer need to hide from predators that happen to absent on their island).

Today, there are no tiny elephants or rhinos, but bovines - where the males of some species can weigh upwards of a ton - are a different matter. At least two, and probably three, species of living bovine are examples of exactly this principle in action.

The reason that I'm vague about the numbers here is that there is still some dispute about the nature of the anoa. There are usually regarded as being two species: the lowland anoa (Bubalus depressicornis), and the mountain anoa (Bubalus quarlesi). But not everyone agrees that the two are distinct. The first formal suggestion that they might be separate species was made by Dutch scientist Pieter Ouwens, better known for being the first scientist to describe the komodo dragon. That was back in 1910, and at least as late as the 1960s, there was still general agreement that the two forms were physically distinct, and that they likely favoured different terrain.

However, as more information on these rare species came in., the picture only became more confused. Both types, it seems, are somewhat variable in form, and features said to be unique to one are often found at least some specimens of the other. Even using genetic data, it can be really hard to tell them apart, and while some studies claim to have found reliable differences, more recent ones have more often muddied the waters than provided any clarity.

If they are separate species, then it would seem that they can interbreed with little difficulty, and there is probably at least some genetic intermixing between the two, even if there aren't any full-blown hybrid populations. Quite what this means for their status as species can be argued, although conservationists do at least agree that there are four distinct populations worthy of protection - even if it's not clear which, if any, of those populations represent species or subspecies.

At any rate, anoa are buffalo, descended from an ancient stock that became isolated on the island of Sulawesi in Indonesia, perhaps about a million years ago. Sulawesi is by no means a small island - it's roughly betweem Missouri and Florida in size, or about 20% larger than Greece. Nonetheless, anoa have become much smaller than their water buffalo relatives on the mainland.

A fully grown anoa stands just 60 to 100 cm (24 to 40 inches) high at the shoulder, and may weigh as little as 135 kg (300 lbs). They are mostly dark-haired, with at least some having white markings on the legs and face. In other respects, though, they quite closely resemble full-sized buffaloes. For example, their horns, while short, are triangular in cross-section, their back lacks any trace of the hump often seen in other cow-like species, and there are also a number of similarities in the form of the skull, and particularly the palate.

The lowland anoa was first scientifically named in 1827 (which, incidentally, means that it's B. depressicornis which stands as the scientific name should there only be one species). At the time, it was simply described as living "on Celebes" - the older name for Sulawesi - without any further clarification. When Ouwens first identified the mountain anoa as distinct, he thought that it lived primarily in the mountainous interior of the island, and it's from this that we get the common names of the two forms.

The reality is, though, that they really don't seem to. It's still not completely clear to what extent the two forms share exactly the same habitat, but they do both live across more or less the same parts of the island. Furthermore, they are both also found on the island of Buton, off the southeast coast of Sulawesi, which is anything but mountainous. Both species live in dense forest, apparently from around sea level to 2,300 m (7,500 feet), avoiding the higher, more sparsely forested slopes. Like many other cow-like animals, they require a fair amount of water, and probably wallow in mud when they get the opportunity. Unusually, they have been reported to drink seawater, although presumably this is as a substitute for suitable salt licks, since it would hardly quench their thirst.

Like much of Indonesia, Sulawesi has a high human population density, with forest being regularly cleared to make way for more farmland. Together with pressure from hunting, this has had a dramatic effect on the anoa population over the last century, and both kinds are formally listed as endangered species. While accurate population figures are hard to come by, there are thought to be less than 2,500 anoa alive today, with the majority of those probably the lowland form. It's likely because of this that the anoa not only stay as far inside the deep forest as they can, but that they are nocturnal, an unusual trait for cattle, but one that helps in avoiding humans.

Our knowledge of anoa biology is understandably somewhat limited. They are thought to browse more, and graze rather less, than their larger relatives, and there is some anatomical evidence for this, although grass still seems to form the bulk of their diet. They are mostly seen alone, and don't seem to live in herds, although, again, this might be an effect of their current low population. From studies in zoos, we know that pregnancy lasts nine to ten months, notably shorter than the eleven and a half months of water buffalo, and that they can live for up to 37 years. In the past, they were apparently a major source of food for the many native species of dung beetle, although the latter have since switched to domestic bovine excrement with little difficulty.

Although anoa are the smallest of all the cow-like bovines, they are not the only insular species, nor even the only dwarf buffaloes. The other species is the tamaraw (Bubalus mindorensis), native to the island of Mindoro, in the Philippines. This is a much smaller island than Sulawesi; at around 4,000 square miles it's half the size of Wales, or a little over half again the size of Delaware. It is, however, even more densely populated, and, rare though anoa are, tamaraw are even more under threat.

Tamaraw are only slightly larger than anoa, having an average shoulder height of about 100 cm (3' 4"). They are dark in colour, with less of the pale markings found in anoa, and horns more closely resembling those of their mainland water buffalo kin, albeit swept back rather than outwards. They once roamed across almost the whole of the island, from open pastures to wooded hills, bamboo jungle, and marshland. They feed mainly on grasses, although this includes particularly large ones, such as bamboo and wild sugar cane.

So far as we can tell from the few examples in captivity, they prefer to be active during the day, although they are increasingly switching to nocturnal habits in the wild, as many endangered animals do. They do not seem as solitary as anoa, but their herds are very small, with rarely more than seven individuals, including at most a single bull and two adult females, with the rest being calves or yearlings. Like other cattle, they give birth to a single calf, probably once every other year, and, like anoa, they have a shortened gestation period compared with their mainland kin, in this case lasting approximately ten months.

During the Ice Ages, tamaraw lived not only on Mindoro, but on the much larger neighbouring island of Luzon. Even at the start of the 20th century, they ranged across most of Mindoro, and were said to number around 10,000. But, in addition to losing habitat to the expanding farms, tamaraw were hunted for both food and sport (as with the anoa, nobody seems to have wanted to turn them into bogus medicines, which is at least something). Legally protected since 1936, they are still subject to illegal hunting to this day, and survive only in three small preserves on the island.

Indeed, around 90% of surviving tamaraw are thought to live in just one of those preserves, Mounts Iglit-Baco, established in 1970 largely for that very purpose. At the last census, in 2005, 269 tamaraw were thought to live there, with another 30 or so divided between the other two preserves. It's likely that the population has dropped further since then, and there may be only around 200 left alive today. They have been classified as a "critically endangered species" since 2000, but the two populations outside Mounts Iglit-Baco may already be past the point of no return, at least for any practical conservation efforts.

Anoa and tamaraw are not the only dwarf buffaloes to have lived. A third species is known from late Pleistocene deposits on the Philippine island of Cebu, and may have been similar in size to the anoa. But the next species I want to cover is something else entirely.

In 1992, the Vietnamese government sent a team of researchers to the newly created Vũ Quang National Park, in order to survey the wild animals living there. While conducting the survey, they came across three sets of horns that belonged to no animal known to science. Follow up visits soon procured complete skulls, as well as more isolated horns. The WWF announced the discovery of a totally new species of large mammal later that year, causing a worldwide media sensation. The following year, after DNA studies had shown that the animal was a new kind of antelope, it was formally written up and named the saola (Pseudoryx nghetinhensis).

It was the first discovery of a totally new and unexpected large mammal since the kouprey in 1937. (Although the Chacoan peccary, previously known only from fossils, was discovered alive in 1975, and arguably might therefore count as well). While we often name new species by raising previously known subspecies to the rank, and new small to medium mammals are discovered all the time, the discovery of something quite so big, and completely unknown is a rare event indeed. Indeed, before the kouprey, there had been only three similar discoveries in the 20th century - most famously, the okapi in 1901, followed shortly thereafter by a pig and an antelope.

At any rate, it was now clear that the saola was some form of antelope, but there still remained considerable doubt as to what sort of antelope it might be. Once they managed to find a living one, it turned out to have a moderately stocky, antelope-like, body, with chocolate brown fur and white markings, and it stood around 84 cm (2' 9") tall at the shoulder. The horns, from which it was first identified, were quite long at 35-50 cm (24 to 30 inches), oval in cross-section, and mostly smooth with a rugged base.

It was originally thought to be a bovine, although probably not very closely related to anything else still living. In 1994, however, a close examination of its teeth and skull showed that it more closely resembled a goat, placing it within the caprine, rather than bovine, subfamily. Others argued that it was so completely weird that it didn't count as anything, and should get a subfamily all to itself.

It was not long before more genetic and physical evidence rolled in, and it became clear that the original proposal had been correct: the saola was a bovine. Not only that, but, despite its appearance, it was more closely related to the true cattle than it was to the bovine antelopes. More recent research to pinpoint its exact placement in the family has indicated that it may be, of all things, a close relative of the buffaloes.

In many respects, the saola is a strange animal, and we know very little about it beyond the purely physical. Those physical features include the presence of scent glands in front of the eyes that are larger than those of any other known bovid, and that are covered by a flap of muscular skin that the animal can consciously raise and lower as it requires. We know that they live in the Annamite Mountains of northern Vietnam and Laos, where they apparently inhabit damp highland jungles, feeding on undergrowth and low leaves.

Part of the problem is that, to date, no scientist has ever seen a live one in the wild. We've taken no less than three camera trap photos, and even observed one caught by the locals, but the saola's natural behaviour largely remains a mystery. They don't seem to associate in herds, except in an August to September breeding season, they apparently like to break saplings by twisting them between their horns (it's not clear why, but perhaps they're marking territory), and judging from a single dead pregnant specimen, they appear to give birth to a single young at a time.

What we do know is that they are yet another species in decline. Their territory is becoming fragmented, making it harder for the surviving populations to intermingle and retain genetic diversity. They aren't hunted deliberately - and, fortunately, traditional Chinese herbalists hadn't heard of them any more than western scientists had, so they aren't used in medicine - but they still end up as incidental captures while hunters are searching for something else. It is estimated that less than a thousand remain alive worldwide, and perhaps less than 250.

Less than 25 years after their discovery, there's a very real risk that they are headed for extinction.

Whatever its exact relationship to other bovines, the saola can be considered an "antelope" simply because it doesn't look like a cow. But, while in its case, that seems to be misleading, there are a great many other bovines that are indisputably antelopes. These belong to two separate branches of the bovine family tree, distinct from that of the Bovini, or "cattle-like bovines". Next time, I'll be looking at some of the largest of these "bovine antelopes"...

[Photo by "Gossipguy", Gregg Yan, and "Silviculture", from Wikimedia Commons.]


  1. Any family tree diagrams for B. mindorensis??

    1. It's shown in the cladogram as "tamaraw".