Sunday, 5 April 2015

The Dog Family: African and Asian Wild Dogs

African wild dog
So far, my survey of the dog family has looked at the "wolf-like" dogs, rather than the foxes and their kin. Most of these are either wolves, coyotes, or jackals, but there are two species that stand slightly apart, although modern genetic analysis has shown that they are, indeed, more closely related to wolves than they are to foxes.

The more distinctive, and probably the better known, of the two species (Lycaon pictus) has a wide number of different names. I'm going to call it the African wild dog here, but it is also known as the "African hunting dog", the "painted dog", or by some combination of these terms. (In French, Spanish, and Italian, it's simply the "lycaon", or some spelling variant thereof. The word commemorates a character from Greek mythology, who Zeus turns into a wolf).

Whatever it's called, the African wild dog is a distinctive animal. The large rounded ears and the slender, athletic body are noticeable enough in themselves, but it's the coat pattern that really makes it hard to mistake for anything else. The exact pattern varies tremendously - every animal is unique, and they can readily be distinguished one from another. Once found throughout almost the whole of sub-Saharan Africa, animals from the north tend to be dark with white and yellow patches, while those from further south are generally pale, with a few black patches. It was once thought that these might represent different subspecies, but they seem to blend into one another gradually as you cross the continent, which would rule that out. African wild dogs are adapted for running, and shedding the heat that results from doing so. They also, for less clear reasons, have no dewclaws on their front feet, as all other dogs do.

Another anatomical peculiarity is that the lower carnassial tooth has an extra blade-like edge on it, where, in other dogs, you'd expect to find a dip. The carnassial teeth are the ones with the greatest role in shearing meat, and the presence of an extra cutting edge implies that African wild dogs are purer predators than most of their kin. This is borne out by observation, too. While most dogs will eat at least some vegetable matter, even if it isn't what they prefer, African wild dogs eat pretty much nothing but meat.

Indeed, while the hunting ability of wolf packs is undoubtedly impressive, African wild dogs are more effective still. Anyone who watches nature documentaries knows that, more often than not, the antelope escapes from the leopard, or whatever might be chasing it. Numerically, most individual hunts end in failure, compensated for by the large haul of meat obtained when they do succeed. But it has been estimated that, for African wild dogs, the hunting success rate is something like 70% - if you're an antelope, and a pack of wild dogs is coming for, your chances of making it out alive are really not good.

The reason that this is so is much the same as the reason why it is necessary: African wild dogs live in packs, that simultaneously have many mouths to feed and a greater opportunity to work together. Cooperation is absolutely key to their lifestyle, and we simply don't find "lone wolves" among them. When grey wolves reach adulthood, the males head off on their own to find a new pack, and so avoid inbreeding with their close relatives. African wild dogs, on the other hand, head off in groups (usually said to be mostly females, although this has been disputed), helping one another until they establish their own pack, or find a larger one to join. They simply can't survive on their own.

This cooperation means that wild dogs can hunt animals noticeably larger than themselves. Their main prey consist of medium-sized antelopes, such as impala, kudu, gazelles, and bushbucks, although they do also attack wildebeest - some of which can be up to three times the weight of any one dog. Smaller prey aren't worth the trouble (although that's not to say that they don't eat such creatures at all if they happen to get in their way), while the truly large animals, such as buffalo, are generally safe once they've reached adulthood. Pack size is, as one might expect, crucial here; the larger the group, the larger the animals they can take down... and the more they need to do so to keep themselves all fed.

There's clearly a balance to be struck here between the number of mouths to feed and the greater success that larger packs bring. Packs that are too small have difficulty surviving, leading to what's called the "Allee effect", in which lower populations lead into a death spiral of ever-declining numbers. One study has suggested that the minimum is around five individuals, with packs smaller than this inevitably doomed if they cannot find partners to bulk up their numbers.

Larger packs aren't just more effective at capturing prey, they are also more effective at holding on to it once they've got it. Larger packs, for instance will drive away hyenas who try to steal their kills, giving them an edge over smaller ones that can only deal with leopards and the like. There are limits to this, and, when faced with a pride of lions, running away is the dogs' best bet, regardless of their pack size. Given their need for a high hunting success rate, this probably explains why the two species are rarely found together.

The optimal pack size seems to be around nine adults plus pups, although packs of up to thirty have been reported. Communication within the pack appears to be highly sophisticated, presumably allowing individual sounds to convey relative subtle meanings (for a dog). For example, African wild dogs have been reported to have a greater number of different "bark" sounds than any other species in the family. Before each hunt, all the dogs in a pack gather round, greeting one another with a chittering call, switching to a softer "hoo" sound that can carry for up to 2 km (just over a mile) once they are running together.

Hunts normally take place at dawn or dusk, or on nights with particularly bright moonlight. Once they have cornered their prey, it is quite common for one dog to grab the victim's nose in its jaws - presumably causing both pain and suffocation - while others attempt to deliver the killing blow. If this is, in itself, an unusual display of coordinated behaviour, an even more remarkable tactic has been shown with zebras.

Here, one dog holds onto the zebra's tail, and another grabs its lip, while the rest attack the underbelly to try and disembowel it. This trick allows the pack to take down an animal that may weigh five times what any one of its members do; an especially sizeable meal. But what's really remarkable is that very few wild dogs seem to know how to do this, and the ones that do belong to the same family lines. A zebra faced with wild dogs will, as a general rule, charge at them, and such is its size that that normally works. But some wild dogs, it seems, have discovered a tactic that gives them the advantage, and pass it on to their own pups. This is, in other words, a sort of cultural tradition, shared by some packs, and not others, rather than an instinctive behaviour.

Cooperation among wild dogs does not end once the hunt is over; it is also crucial to raising their young. As with most dogs, the core of the pack is a mated pair, and any subordinate female that becomes pregnant usually won't be able to obtain the support she needs to raise her pups. The mated pair are dominant, with each sex maintaining its own hierarchy within the pack.

The mother gives birth in a den, often pinched from an aardvark, with the rest of the pack protecting her. The reason that subordinate females so rarely succeed in breeding is that wild dog litters are unusually large, and require a lot of care and attention. About ten to twelve pups is considered average, but the maximum may be as high as twenty. No mother can expect to raise all those pups on her own, and, once again, the larger the pack, the better everyone is going to do.

Everyone tries to help look after the pups, fostering them in a way that is rarely seen in other non-primate mammal species. In fact, the drive to help one another is so strong that it extends beyond just the pups. Adults returning from a hunt will disgorge food for young pups, whether they are theirs or not, but, unusually among dogs, they will do it for other adults as well, if the latter would otherwise have gone hungry (perhaps due to infirmity).

That this unusually cooperative lifestyle, combined with what appears to be a high intelligence, succeeds, is shown by the fact that wild dogs are found across such a large swathe of Africa, and in every habitat save desert, high mountains, and dense jungle. Nonetheless, they are an endangered species, due as much to the expansion of human agriculture as anything else. They do not, on the whole, seem to attack livestock, preferring wild antelopes, but, if anything, keeping to the wild is a disadvantage, as suitable land becomes more and more fragmented, cutting breeding populations off from one another. The species has already gone from western Africa, and around half of the 6,000 or so wild dogs alive today (most of them not adults) are in the south, in Botswana, Tanzania, and Zimbabwe.

Dholes
The remaining species of "wolf-like" dog is also endangered, and may have a surviving population as low as 2,500. This too, has a number of names, among them "Asiatic wild dog", but it is most commonly known in English-speaking countries as the dhole (Cuon alpinus). Dholes inhabit forested regions of China, India, and Southeast Asia, with a distinct subspecies on the islands of Sumatra and Java. They look much more wolf-like than African wild dogs do, but are smaller, with a reddish coat and white markings.

If African wild dogs have a reputation for cooperation and intelligence, the reputation of dholes is as rapacious killers, almost demonic in their bloodthirsty destructiveness. In the west, this is largely down to how Rudyard Kipling portrayed them in the second volume of The Jungle Book, but, in fairness, he was basing this on their pre-existing reputation in India, where they are apparently known as (among other things) the "hounds of Kali".

The truth, of course, is rather more benign. Dholes are no more bloodthirsty than other dogs, and even supplement their meaty diet with a small amount of vegetable matter. Their prey consists largely of deer, especially sambar and muntjacs, although they also eat other hoofed animals, such as goats, bovines, and wild boar, and the occasional smaller animal, such as wild chickens. When times are hard, they scavenge for carcasses, sometimes even eating fallen animals as large as Asian elephants. Like African wild dogs, their teeth differ from the usual canid pattern, although in this case, the differences - a different shape to the carnassials, and the absence of the last pair of lower molars - provide a less clear evolutionary advantage.

Dhole packs typically consist of about five to ten adults, and they hunt mostly during the day, when deer are easier to find. While they don't reach the levels of African wild dogs, their hunting style is notably cooperative, and may include some pack members flushing out prey while others lie in ambush, and tactics such as driving deer into water to attack them. Like wild dogs, they carry food back to any pups that they have, sharing it out among the group.

Packs normally have many more males than females, apparently because it is the females that leave the pack on adulthood, travelling alone for a while, or in pairs, before finding a new one to join. As with African wild dogs, dholes have an unusually complex vocal repertoire, which may be able to convey a wide range of different meanings. At least eleven different calls have been identified, one of which, a two-syllable whistle used to maintain contact in dense cover, is unique to each individual, allowing pack members to tell one another apart by sound alone. (This unusual sound is notable enough that one of the many names for the animal is the "whistling dog").

Dholes breed much as other dogs do, with a much more normal-sized litter than that of African wild dogs. Like those animals, however, all the pack helps to look after the pups, although perhaps not to quite such an extreme level, allowing smaller packs to survive without too much difficulty.

African wild dogs and dholes were once thought distinctive enough from other dogs, and similar enough to one another, to form their own subfamily. We now know that they are successive branches at the base of the "wolf-like" part of the dog family tree, with dholes closer to jackals than they are to wild dogs. As such, they complete my look at the truly wolf-like dogs, and while not every other species can meaningfully be described as a "fox", they are at least more fox-like than anything else. It therefore makes sense to continue our review by looking at the first animal most people in the Northern Hemisphere likely think of when they think of a "fox"...

[Photos by Philip Gabrielsen and Fabrice Stoger, from Wikimedia Commons. Cladogram adapted from Lindblad-Toh et al, 2005 and Bardeleben et al, 2005]

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