Sunday, 7 August 2016

Bovines: The Largest Living Antelopes

Common eland (male)
Over the last few months I have looked at the various species of cow-like bovine, including such creatures as yak, bison, and water buffalo. But we've known, since at least the 1950s, that there are also a number of other animals that are more closely related to cattle than they are to other kinds of bovid. Although the choice of terminology is ultimately arbitrary, these are commonly considered to be members of the subfamily Bovinae, and thus can also be described as "bovines".

They are not, however, physically very cow-like, and so are instead described by the more generic term "antelope" - which really just means "any bovid that's not obviously some kind of cow, sheep, or goat". The great majority of antelopes are therefore not "bovines" in any sense, belonging to their own distinct subfamilies. The majority of those that are are commonly referred to as spiral-horned antelopes. While all bovines are said to have some degree of spiral growth pattern to their horns, it's only in these antelopes that it's really obvious, with multiple turns of the spiral clearly visible to the observer.

These animals are typically much smaller than cows, and, because of their slimmer build, do typically match our common image of an "antelope". However, there are two species that are exceptionally large, overlapping with some of the smaller cow-like bovines. And, if you bulk an antelope up enough, it starts to look like a cow, so in these two species the bovine relationship is, perhaps, rather more visibly apparent than it is in the others.

In fact, these are the largest living species of antelope in the world.

By far the more widespread of the two is the common eland (Taurotragus oryx). The first half of that scientific name literally translates as "bull-goat", and one can see what Johann Wagner was thinking of when he came up with it. Elands are large and heavily built, with a hump over the shoulders similar to those seen in in many more cow-like animals, and both sexes have a prominent dewlap. The males average 163 cm (5'4") at the shoulder, and weigh about 600 kg (1,300 lbs) - about double the weight of even the largest wildebeest. Of course, that's the average, and males weighing nearly a ton have been recorded, although at around 142 cm (4'6") and 400 kg (890 kg), the females are quite a bit smaller.

Common elands are found across pretty much the whole of Africa south of the equator, saving only the dense jungles of the Congo and the barren deserts of the Kalahari.They inhabit open wooded country, such as savannah, and all but the most treeless of grasslands. They can be found at quite high altitudes on lightly forested slopes up to 4,600 m (15,000 feet) in elevation, and will certainly wander into farmland if there's nothing to stop them.

Common eland (female)
Perhaps surprisingly, they don't seem to need a lot in the way of water, apparently being rather good at retaining what they do drink, so you don't tend to see great numbers of them gathering around water-holes as so many other large African animals do. They're mostly active during the daylight hours, being quite tolerant of heat, but will forage for food at night if it's really, really, too hot to do much during the day.

One clear difference from the more bovine bovines is that elands have a narrower snout, rather than the broader, shorter, faces of cattle. This implies that they are more likely to be browsers, picking out tasty leaves with a degree of precision, rather than just scooping up whatever grass happens to be nearby. However, they have generally been considered to be "mixed feeders", perhaps browsing animals that have adapted to a more grazing diet in the relatively recent evolutionary past. However, it has been noted that they really only seem to eat grass when it's at its freshest, early in the rainy season, so it's probably fair to say that they prefer moderate quantities of nutritious food to large volumes of lower quality forage. The rest of the time, they feed on leaves and seed pods, and they can apparently dig for tubers with their horns.

Elands are, of course, herd animals, and can aggregate in remarkably large groups, in some cases with up to 500 individuals. However, that's very much a maximum, because they really don't seem to show any loyalty to their herd mates, and, unlike most antelopes, are not at all territorial. The females, in particular, wander across huge areas, of up to 420km2 (160 square miles), but they don't necessarily do so together, and join up with whichever other elands they happen to come across. Once they're weaned, even the younger animals don't seem particularly attached to their parents, wandering off from their mother to hang about with others of their own age in herds of a dozen or more. The result is a sort of nomadic lifestyle, shaped by the local availability of food and by the fact that, being so large and heavy, elands are also said to be the slowest-moving of all antelopes. This latter may also explain why the older males can't be bothered to migrate much, and tend to stay put, so long as there's ample food around.

Having said which, if you can force the females to stay together for long enough to evaluate them, they quickly form a dominance hierarchy, with older individuals typically having the most clout, and family relationships being more important than, say, mere physical prowess. Presumably, given that they don't live like this in the wild, their natural behaviour is considerably more complex. (It also has to be said that keeping them in captivity isn't exactly easy - the younger ones can apparently jump over a 3-metre fence from a standing start, while the older ones will just walk straight through anything that isn't especially sturdy).

Elands seem to breed throughout the year, although there is a slight tendency to synchronise births for the start of the rainy season when food is most plentiful. Females signal their readiness to mate with hormones in their urine, and also frequently urinate when pursued by an ardent male when they're not in the mood - the male will sniff the urine, realise from the absence of hormones that he's not in luck today, and give up. (This contrasts with smaller and faster antelopes, like impala, where a female in the same situation will just run like heck until the male either gets the message or fails to find where she's got to).

When the females are ready to mate, however, the males compete with another by head-butting and wrestling with their horns. The horns have the clear spiral pattern for which the larger group of antelopes that elands belong to are named, and are particularly stout and thick in the males. However, females have horns too, and theirs are actually longer at around 60 cm (2 feet), albeit rather narrower. In their case, it seems, they use them, not to wrestle with others of their kind, but to stab predators after their calves.

As with most antelopes, newborn elands are able to stand almost as soon as they are born. They join communal nursery groups as soon as possible (this can sometimes take a couple of weeks, if the mother has wandered particularly far from the rest of the herd before giving birth), and, while they are not fully weaned for six months, start to take at least some solid food almost immediately. The horns grow rapidly enough, and steadily enough, to be good estimators of age in young animals, although this naturally stops working once they reach adulthood. Elands can live up to 25 years in captivity, although probably not more than 20 in the wild.

There is some dispute as to whether or not there are identifiable subspecies of common eland. Three are most commonly listed, and individuals from the north have a blander, greyer, coat, than the more striped, brownish, coats of those further south, but it's not clear whether these differences are truly distinct, or just blur into one another gradually across the animal's range. There is, however, no dispute that there is an entirely separate, second species, of eland: the giant eland (Taurotragus derbianus).

Despite the name, this is actually more or less the same size as the common eland; some sources say they are slightly smaller than the common species, although most say the opposite. Either way, the difference is small, with far too much overlap between the two to be useful as a means of distinguishing them. The giant eland's horns, however, are much bigger and more solid than those of its common relative, and are larger in the males, reaching a whopping 120 cm (4 feet) in length in the largest individuals. It may well be these, rather than body size, that are the original source of the epithet "giant".

Giant eland
Otherwise, the two species do look rather similar. Compared with the common sort, giant elands have larger, more rounded ears, a more prominent shoulder hump, and a larger and differently-shaped dewlap with a long fringe of hairs. They live further north, with one population in Guinea and Senegal, and another in Cameroon and the Central African Republic. (These may, or may not, be different subspecies, depending on who you believe). They also seem less adaptable than common elands, being found only in heavily wooded areas, although not truly dense forests. This is probably related to their diet, which seems to consist almost entirely of leaves, shoots, and fruit, and to include hardly any grass at all.

This narrower diet and preference for particular habitats may explain why giant elands don't travel as far as the common sort, since they tend to stay where they know there is good food. Similarly, their herds are smaller; although they can sometimes reach as many as 60 members, 15 to 25 is more common. They can also run faster than common elands, although, oddly enough, they may have less need to, since even a lion would think twice before attacking a full-grown adult (the sick and the young are, as always, a different matter). In most other respects, the two species are probably very similar.

It is thought that giant elands once lived across the entire band of territory from Senegal to South Sudan. Certainly, there is nothing in the habitat or climate there that would prevent them from doing so. Today, however, they are restricted to the two patches of territory I mentioned above. Much of this is due to hunting, either for meat, or to keep their spectacular horns as trophies. Advancing agriculture is likely also a problem, particularly since they seem especially vulnerable to rinderpest, a disease of cattle. Fortunately, even with the added problems of political instability, there seem to be more than enough of them in the eastern population for the species as a whole to be quite secure.

The western population, however, is in a far more perilous state, with less than 200 individuals thought to survive in the wild. A captive breeding program in the Niokolo-Koba National Park in Senegal has shown some success, although the small number of animals involved is leading to some genetic inbreeding.

No other spiral-horned antelope have has horns quite so tightly twisted as those of the elands, with most having no more than a single 360-degree turn along their length. In two closely related species, however, the spirals still manage to be quite impressive, and it is to those that I will turn next...

[Photos by "PJ KAPDostie", Lip Kee, and Niels Elgaard Larsen, from Wikimedia Commons. Cladogram adapted from Bibi 2013 and Stankowich 2009.]

Synapsida will be taking a summer break next week, but will return 21st August.


  1. Re:
    "common eland (Taurotragus oryx). The first half of that scientific name literally translates as "bull-goat""
    …and I think the second half of the common name is Dutch for elk. (If so, it is easy to see what the early Afrikaners were thinking, too: "This is a horned artiodactyl larger than any others here: so let's re-use the word for the larges horned artiodactyl in Europe.")

  2. Re the susceptibility to rinderpest - as of 2011 the disease has officially been declared extinct worldwide after a global eradication and vaccination campaign, so hopefully this will be good news for Africa's wildlife