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.
Banteng are generally smaller than animals like bison or wild yak, standing 'only' around 160 cm (5' 3") tall at the shoulder, and weighing 600 to 800 kg (1,300 to 1,800 lbs). They are also somewhat slimmer, with longer legs, although nowhere near enough for them not to be obviously cattle-like. While both sexes have pure white legs, the females are otherwise brownish-red in colour, while the males, which are generally larger, vary from dark brown to near-black, depending on the subspecies. The males also have larger horns, which are united at the base by a band of horny tissue that runs across the top of the skull.
Much of what we know about wild banteng actually comes from that Australian population, which is not only more numerous, but also rather more accessible than those populations still hiding in the places like the Vietnamese jungle. We do know that they are forest-dwelling animals, as most wild cattle are, which probably explains why they haven't left that one patch of land in Australia - it's surrounded by open plains. Given the opportunity, they feed primarily on grass, with a side order of shrubs and other vegetation when that is in short supply. Breeding takes place at varying times of the year, depending on locality, but typically between March and June (although not in Australia, for some reason), with a single calf being born 285 days later.
They live in relatively small herds, of up to about twelve individuals, which are sexually segregated outside of the breeding season, although they sometimes gather into much larger groups where food or water is particularly plentiful. Often thought of as lowland animals, they have been seen as high as 2,100 m (6,900 feet) in elevation, although this could well be due to the replacement of their preferred habitat with agricultural land.
Banteng have probably been domesticated since about 3,500 BC, and they are primarily used as beasts of burden and sources of meat, rather than as milk cattle. Today, something like a quarter of the "cattle" in Indonesia are actually banteng, with the majority being in southern Sumatra, Sulawesi, Java, and, of course, Bali. They are said to be more resistant to disease than true cattle, better able to survive on low-quality food, and to be more fertile (although the latter is balanced by a low survival rate of calves in times of hardship). On the down-side, their hooves are said to be softer than those of true cattle, which is fine if you're working in a paddy field, but less so if you have to use modern paved roads.
The picture is complicated somewhat by the fact that banteng are, like many members of the genus Bos, capable of cross-breeding with domestic cattle, although the resulting males are often sterile. The Madura breed of cattle, found in Indonesia, are an example of such a hybrid, while as many as 65% of a supposed population of Bali cattle in Malaysia turned out to have at least some domestic (zebu) cattle ancestry. Nonetheless, many Bali cattle - especially in, for example, Bali - are essentially pure-bred banteng, and with nearly 3 million of them employed in agriculture, the species as a whole cannot be said to be at risk.
But, as noted above, this is very far from the case if we look only at the remaining wild animals. In 2008, the world population of wild banteng was estimated as being no higher than 8,000 individuals, and probably much lower than that. They are restricted to small, relatively isolated populations, scatted across Indonesia and southeast Asia. Few of these populations have more than about 50 members, and most of those that do are on Java. While Thailand seems to host the largest remaining population on the Asian mainland, in Vietnam, for example, there are likely no more than a hundred left alive, and that number is dropping.
Loss of habitat is, as so often, part of the reason for this. With its extremely dense population, Indonesia does, after all, have a lot of farmland, and the forests are retreating as it expands. However, it seems likely that hunting is more of an immediate threat to wild banteng, with habitat loss exacerbating an already existing problem. Much of this hunting is for bushmeat, but the horns of banteng are also valuable, both as trophies and, in some cases, for traditional medicine (why the horns of domestic banteng are unsuitable for the latter I have no idea, but then, traditional medicine rarely relies much on logic). Attempts to save the species using controversial techniques such as cloning and inter-species nuclear transfer have been made, but have so far met with no lasting success.
This tale of wild cattle becoming rare even as their domesticated relatives thrive is one that's likely familiar by now. It's true of both yak and gaur, not to mention true domestic cattle, whose wild ancestor is entirely extinct. Neither of the two species of bison have exactly done well, either. Which brings to the one remaining species of Bos which I haven't covered yet, which happens to be one that was never domesticated at all.
Which, as it turns out, was really not good news for the kouprey (Bos sauveli).
Kouprey are larger than banteng, if not quite as large as bison, reaching 180 cm (6 feet) at the shoulder, and weighing up to 900 kg (2,000 lbs, or a US ton). They are grey in colour, with the males being darker than the females. Males are also distinguished by having a dewlap that is so large that it almost reaches the ground in particularly old individuals, and long horns that have frayed brush-like tips formed of shredded keratin. Such fraying has been seen on the horns of some European bison, but never to such an extent, and what (if anything) its purpose might be remains a mystery. Females, on the other hand, have smaller horns, but ones in which the spiral pattern of growth is much more apparent than it is in other cow-like bovines. So far as we know, the habits and biology of kouprey are much the same as those of banteng or gaur.
But the fact is, we know very little. Kouprey were only discovered (by scientists, that is, not the locals) in 1937, and have not been seen much since. It later turned out that there had been a stuffed one sitting in the Museum of Natural History in Paris since 1871, on the basis of which it was later claimed that kouprey might have been domesticated in Cambodia at some point. So far as I can tell, there isn't much supporting evidence for this theory, which looks circumstantial at best.
The real debate about the kouprey however, has been as to whether it is actually a species at all. The possibility that it wasn't was first raised in 1947, when it was instead proposed that it was actually a hybrid between banteng and... well, something... maybe a domestic zebu ox, maybe a gaur, maybe even (somewhat implausibly) a water buffalo. But, you know, definitely something. The suggestion did not receive much attention at the time, and neither did a later study, in 1958, that narrowed the possibility down to a banteng/zebu hybrid. In 2006, however, the question hit the scientific headlines when a genetic study appeared to confirm that it was true: kouprey really were just the result of a relatively recent cross between banteng and domestic cattle.
The story received a fair amount of publicity, at least by the standards of such things, even though it was almost immediately questioned. More genetic analysis followed, this time showing fairly conclusively that the kouprey had been a naturally occurring species all along. Apparently, at some point back in the Pleistocene, kouprey had bred with the mainland subspecies of banteng, leaving behind a small but significant genetic signal that had confused the results of the earlier test.
Another mysterious bovine from the region was not so lucky. In 1993, horns of a previously unknown species of animal were uncovered in Vietnam. Without the rest of the animal for study, it wasn't initially clear what sort of animal it was - gazelles and goats were both suggested - but its similarity to kouprey eventually led to the conclusion that it was some kind of bovine. Named as the linh duong ("Pseudovibos spiralis"), genetic analysis seemed to confirm that it was most closely related to buffalo, and that it had been known to the Chinese since at least the 17th century. Except, as it turned out, the specimens were fakes, actually derived from domestic cattle. The linh duong, unlike the kouprey, never existed.
Unfortunately, the kouprey faces a threat far more serious than mere taxonomic oblivion. In 1988, it was estimated that no more than 300 koupreys remained alive in the world, mostly Cambodia, with smaller populations in Vietnam and Laos. It is now generally agreed that that figure was a gross overestimate, and the animal is officially listed as "Critically Endangered", meaning that, since there are none in zoos, it is on the very verge of total extinction.
As with banteng, hunting is far more a pressing issue for koupreys than the more usual suspect of habitat loss. They are regularly hunted for their horns, mostly for use as trophies... or, at least, they were, since none appear to have been available for sale since the 1990s, and they weren't necessarily new then. It is clear from the surveys we have been able to do that koupreys do not survive in Vietnam, Laos, or even in western Cambodia.
As for eastern Cambodia, where they were traditionally the most numerous, a couple of zoological expeditions to the area in 1969 reported seeing only a very small number of the animals. Since then, nothing. There has been the occasional anecdotal report, but none of them backed by any hard evidence; so far as we know, nobody has seen a living kouprey in over 40 years.
It's just about possible that a few individuals remain, perhaps sheltering with small herds of banteng, or more likely living alone. If so, it's almost impossible to imagine that the population is large enough to be viable. And, to be honest, given the length of time involved, it is far more likely that the kouprey, its official status notwithstanding, is already completely, and finally, extinct.
That sad note brings me to the end of the genus Bos. There is, however, a second group of genuinely cow-like bovines, and it is to those animals - the buffaloes - that I will turn next.
[Photo by "Rushen", from Wikimedia Commons. Cladogram adapted from Bibi 2013 and Stankowich 2009.]