Saturday, 28 November 2015

The Dog Family: Raccoon Dogs and the Fate of the Warrah

Raccoon dog
The Wikipedia page on the dog family includes, on its attached discussion page, a complaint that the article includes a picture of a raccoon - an animal that is clearly not part of the Canidae. Except, of course that there isn't (and wasn't then) any such picture. The complainant was looking at a picture of a raccoon dog.

It's an understandable mistake. The raccoon dog (Nyctereutes procyonoides) does look remarkably like its partial namesake. Indeed, the second half of its scientific name, first given to it by John Edward Gray in 1834, actually means "raccoon-like". The effect is achieved primarily by that dark mask over the eyes, a feature we naturally associate with raccoons, although, aside from the lack of stripes on the tail, the rest of the animal is fairly raccoon-coloured as well.

Nonetheless, it is indisputably a dog, although quite how it was related to other dogs was long a source of puzzlement. Modern studies have shown that it appears to be related to the true foxes, albeit not very closely. Its closest relative may, in fact, be the bat-eared fox of Africa, although, again, I should stress that this isn't exactly what you'd call a close relationship... just closer than anything else happens to be.

Raccoon dogs are native to the Orient, where they are found through much of China, in Korea, Japan, and neighbouring parts of Southeast Asia and Far Eastern Russia. They are perhaps best known from Japan, where they are known as "tanuki", a name sometimes adopted in English as a less ambiguous alternative to "raccoon dog". There may in fact, be two different subspecies in Japan, one on the main islands, and a physically smaller one on Hokkaido, although many authorities group them together. Either way, evolutionarily speaking, they seem to be relatively recent offshoots of one of the mainland subspecies.

But the most widespread of the subspecies today is N. p. ussuriensis, found naturally in Manchuria and Russia. Over a thirty year period, starting in 1928, Russian fur-trappers began transporting some of these dogs to the western parts of what was when the Soviet Union. The raccoon dogs, it turned out, had no respect for national boundaries, or even the Iron Curtain, and began to spread further west. Today, there are significant populations of wild raccoon dogs throughout much of eastern Europe, as far west as Sweden and Germany, and as far south as Bulgaria. (The founder population, incidentally, was large enough that inbreeding didn't become a problem). A few have even been spotted wandering over the border into countries like France and Switzerland, although they don't seem to have established stable populations there.

The reason for the value of this subspecies is that it develops a particularly thick pelt in winter, so much so that it looks even stockier and short-limbed than it already is, perhaps enhancing the "raccoon-like" effect. In any event, raccoon dogs are not particularly large, being about the same shoulder height as a basset hound, but, since they have proportionately longer legs, being considerably lighter.

Like their relatives the foxes, they are omnivorous, and will eat just about anything, which, in practice, means that much of their diet consists of rodents and fruit. The Japanese subspecies, at least, has even been seen climbing trees to get at fruit, something rather unusual in a dog. Nonetheless, they are opportunists, and, if, for example, frogs happen to be particularly common where they are, frogs are what they will eat.

For the most part, they are forest dwelling animals, but, being as willing to vary their diet as they are, they don't seem to mind much what sort of forest it is. For that matter, agricultural land doesn't seem to bother them, and they even wander into the edges of urban areas in Japan, perhaps because of the availability of edible refuse. They are primarily nocturnal, although they certainly can be active during the day, and don't seem especially territorial, compared with other dogs. They live, as foxes do, in mated pairs, and, so far as we can tell, these bonds last for life, with an individual seeking out a new mate only if their partner dies.

In one respect, however, they are completely unlike foxes, or, for that matter, any other living species of dog: they hibernate.

Well, all right, "hibernate" is perhaps a bit of an exaggeration, but not by much. As the autumn approaches, raccoon dogs begin to stuff themselves with food, building up fat reserves. Blood analysis of animals at this time of year shows a sharp rise in the levels of ghrelin, the hormone responsible for the feeling of hunger in mammals, and which also diverts excess energy into fat. This in turn, is apparently under the control of melatonin, a hormone whose production changes with the length of the day, providing a seasonal "clock" as the winter draws near.

Once the days are short enough, however, ghrelin production plummets, and other hormones take over, switching the animal's metabolism to burning fat. Over the next two months, the raccoon dogs lose over 40% of their body mass, and enter a period of dormancy similar to that of bears. Their body temperature also drops by a degree or two to conserve energy, although by nowhere near enough to qualify as the sort of true hibernation we find in, say, bats. Although they do wake up from time to time, and more frequently than bears do, they are asleep through much of the winter, which is more than can be said for any other dog.

Mating occurs in March, not longer after they've woken up from the winter sleep. In fact, it seems that the dormancy actually helps them, with farmed animals fed through the winter having less pups than those that are basically starved for two months - clearly raccoon dogs are finely tuned for the way that they normally live their lives. Raccoon dogs in Japan have litters of five or six pups, but those in Poland average about eight, something that seems to be a subspecies difference, rather than anything to do with the local climate. Both parents care for the pups, which doubtless goes a way to explaining why they are so faithfully monogamous in the first place.

Over the last year, I have, counting the disputed red wolf, described all 35 of the living species of dog known to exist as of January 2015. I have to add that last qualification, because, remarkably, a new one has been discovered since I started: the golden wolf (Canis anthus). These were previously thought to be golden jackals, representing the African population of those animals - which are otherwise found in Asia. A new genetic analysis published in August of this year showed that they are actually closer to wolves and coyotes than they are to other jackals, but that, nonetheless, they aren't quite grey wolves either. Given how long it took us to notice this, you probably won't be surprised to discover that they're very similar to golden jackals in most respects, although they are said to have a higher forehead and a narrower snout.

Of those 35 (now 36) species, five are considered to be endangered: African wild dogs, dholes, Ethiopian wolves, red wolves, and Darwin's fox. The last two of those are "critically endangered", literally on the brink of extinction. But there is one other dog we should talk about, a dog that has, in recent historical time, fallen over that brink. The one modern species of dog that is already extinct.

When the Falkland Islands were first discovered by Europeans in 1690, the explorers were somewhat surprised to discover the presence of wild dogs there. It was particularly surprising in light of the fact that were absolutely no other land-dwelling mammals on the island. Normally, when you find remote islands with only or two species of mammal, you expect them to be mice or bats, or something like that, not an animal the size of a small wolf.

But that was what they had found, and it became known as the "Falkland Islands wolf", or warrah (Dusicyon australis). They were dark-furred creatures with a white throat and a white tip to the tail, and, while no specific records exist, we must assume that they inhabited open heath and scrubland, given that there isn't much else on the islands. They have been found nowhere else, except on these two remote and desolate islands, leaving open the question of how on Earth they got there.

There have been no shortage of theories. Were they perhaps just feral dogs, brought across by Native Americans? No, because, firstly, they really do appear to have been a separate species, and secondly, so far as we can tell nobody ever reached the Falklands before Europeans did - there is no vanished tribe that could have been responsible. That also scuppers the idea that they were the feral descendants of an entirely separate domestication incident, as was being proposed as recently as the 1970s.

For a long time, it was thought that they surely had to be related in some way to the South American foxes, although Charles Darwin, when he visited the islands on the Beagle in 1834, noted that they looked quite different. (As one example, all South American foxes have a black tip to the tail, but the warrah a white one). Darwin's objections aside - and he was really only saying that they weren't the same species as the culpeo, which he had seen - for much of the twentieth century South American foxes were placed in the same genus, Dusicyon, as the warrah, suggesting a very close relationship.

The mystery was really only solved in 2009, when it was discovered that the creature they were most closely related was, to pretty much everyone's surprise, the maned wolf. Having said which, their ancestors appeared to have diverged from those of the maned wolf something like six million years ago, which is even before dogs had reached the very northern bits of South America, let alone anywhere near the Falklands.

There are, as it turns out, fossils of very similar dogs from Patagonia, which may have died out as recently as the third century AD, and were certainly there since the time of the Ice Ages. This still leaves open the mystery of how they got to the Falkland Islands, which, even when sea levels were at their lowest during the Pleistocene, were still quite some distance from the continent. (Albeit, at that point, much larger than they are now, and united into a single island).

By comparing the DNA of warrahs with those mainland relatives of theirs, we can at least say that whatever happened, it likely did so around 14,000 BC. That's during the Ice Ages, and it's possible that, at least some of the time, the seas that far south were frozen over. Maybe the warrah reached its home by crossing not a land bridge, but one made of ice.

Their long subsequent isolation left them entirely fearless. They had no predators, and, when humans turned up, no reason to run from them. According to accounts, they would walk right up to someone holding out a piece of meat for them... until that person smashed them over the head or stabbed them to death, whether for their fur or out of fear that it would attack their sheep. (Which they probably didn't, never having hunted anything even close to the size of a sheep for many thousands of years).

It is generally agreed that the last warrah was killed in 1876, at Shallow Bay on West Falkland.

[Photo by Piotr Kuczyński, from Wikimedia Commons. Painting by John Gerrard Keulemans, in the public domain.]

1 comment:

  1. It would be interesting to discover if a precise date for the shooting of the last wild Warrah is known, as it may actually be prior to the date the last captive individual died - 2 March 1876, at London Zoo, the last of four specimens to come to the collection over the course of the 19th century.

    By the by, it may also be worth noting that since the 1987 study cited by yourself which suggested the Japanese Raccoon Dog evolved recently from mainland stock, further studies have suggested that the taxon may merit full species status due to chromosomal and morphological differences from mainland Raccoon Dogs, most recently Kim et al (2015):