Sunday, 8 February 2015

The Dog Family: Coyotes and Red Wolves

Grey wolves are found across the Northern Hemisphere, but they originated in Asia, only reaching the Americas via the Bering land bridge when sea levels were low. Most of their close relatives are also found in the Old World, but there are one or two very closely related species in North America. Of these, by far the more common and better known is the coyote (Canis latrans).

Coyotes first evolved, in North America, during, or shortly before, the Ice Ages, almost certainly from the now-extinct Pliocene species Canis lepophagus. Today, they are found throughout almost the whole of North America, from Alaska to Panama, being absent only from eastern Canada, the Caribbean coast of Central America, and a number of islands. In this respect, they have actually benefited from the presence of humans; before the arrival of Europeans, coyotes did not live anywhere along the east coast of America, and only moved in once we started chopping trees down to make way for cities and farmland.

Having said that, like wolves, coyotes are adaptable animals that seem happy to live just about anywhere. Coyotes live on the wide open spaces of the Great Plains, in mountainous and hilly terrain, in deserts, forests, and tropical jungles. Not to mention that, in more recent times, we even find them in urban areas, where they can take advantage of the ready presence of human garbage. This, it should be noted, is something that wolves do not do, which is they are restricted to wilderness, while coyotes are willing to put up with humans if they have to.

Coyotes are noticeably smaller than wolves, weighing between 7 and 20 kg (15 to 45 lbs) when fully grown, about half the weight of an adult wolf. If it stands over 60 cm (2 feet) tall, and is more than about 130 cm (4' 6") long, it's a wolf, not a coyote. Coyotes also typically have brown or reddish fur, compared to the greyer colour of wolves.

But neither of these are definitive guides to telling the two apart. For one thing, even if you can accurately gauge their size at a distance, not all wolves are going to be fully grown. More significantly, perhaps, some coyotes, especially those native to mountainous terrain, can be just as grey as wolves are - and, for that matter, some wolves are brown. The shape of the head is a much better guide to which is which: compared with wolves, coyotes have a narrow, pointed snout, and large triangular ears, instead of smaller rounded ones.

Perhaps surprisingly, coyotes were not scientifically recognised as distinct from wolves until as late as 1823, when naturalist Thomas Say described them in an account of an 1819 expedition from Pittsburgh to the Rocky Mountains led by explorer Stephen Harriman Long. It's hard to imagine, even considering that they weren't yet found on the east coast, that nobody European had noticed them before then... but perhaps they didn't have a scientist with them at the time.

As their presence in urban areas testifies, coyotes are willing to eat just about anything that moves, and a fair few things that don't (about 10% of their diet in the wild is vegetable matter). Being smaller than wolves, however, their most common prey are things like rodents and rabbits, along with young deer and the like. When they do eat larger animals, it is often as carrion, rather than something they've taken down themselves. Having said which, coyotes certainly will hunt and kill relatively large animals when they get the opportunity, as many livestock owners in the United States know only too well.

When it comes to catching things like mice, coyotes hunt on their own, but they do cooperate when searching for larger prey, and they are, like most dogs, social animals. Coyote packs have the same structure as those of wolves, with a dominant mated pair, and a number of non-breeding youngsters. However, they do seem to be more dedicated to monogamy, with a given mated pair staying faithful to one another for the whole of their lives (which, incidentally, is typically no more than a decade in the wild). In places where much of their prey consists of things like elk, coyote packs can have as many as ten members, but they're usually smaller, and lone individuals, mostly male, are common, prowling around in search of a pack to join.

With the mated pair at the top, there is a strict hierarchy within the pack, and pups start fighting with one another to establish dominance from about the age of three weeks. The dominant members get the first choice of food, keeping, for example, large sources of carrion to themselves and forcing younger coyotes to go out and search for mice instead. For the most part, coyotes are active around dawn and dusk, but, as with many animals, they become more nocturnal where humans are around.

Packs are highly territorial, defending an area of up to 25 square miles (65 km2) - although usually much less - from others of their kind. The territory is maintained by a combination of leaving scent marks at the boundary, and fighting any other coyote that tries to enter, along with the odd bit of howling. Although all coyotes scent mark, the mated pair in any pack performs the great majority of the work. Within the mated pair, the male does more of the fighting, and seems mainly interested in driving rivals away from his partner, while the female is more concerned with ensuring a steady supply of food and somewhere safe to rear her young.

Solitary coyotes don't bother with a territory, and only scent mark occasionally, presumably just to indicate that "hey, I'm around, and, if anyone of the opposite sex might be interested, I'm getting kind of lonely here." Should they have the misfortune to stumble upon a pack's territory - and they seem to manage it more often than the established packs might like - violence is likely to result. In such cases, the intruder usually beats a very hasty retreat, and it is quite rare for things to escalate far enough for blood to be drawn.

Lone coyotes are also, of course, known for doing quite a lot of howling to advertise their presence. But they're by no means alone in this, as packs also howl, both as warnings to outsiders and greetings to one another. The scientific name Canis latrans literally means "barking dog", and it has to be said that coyotes are highly vocal animals, barking, yelping, whining, and making pretty much any other noise that one might associate with dogs, and for almost any reason one could think of.

Females come into heat once a year, some time between January and March. Pregnancy lasts 63 days, which is basically the same as in wolves and dogs, and results in a litter of, on average, six pups. Before birth, the mother establishes a den in some safe location, sometimes going as far as to pinch the burrow of another animal, but more commonly sheltering beneath overhanging rocks, inside hollow logs, or among dense vegetation. The young remain there for about three weeks after birth, and are weaned a month after that.

Red wolf
At the start of this post, however, I said that there are "one or two" species in North America closely related to the grey wolf. Why was I so vague about the number? Well, it's because there is still some debate as to whether or not the other one really exists. Not that anyone doubts that there is, physically, such a thing as the red wolf (Canis rufus), but because it's not so clear-cut that it's really a species.

Red wolves have the same shape to the head and ears as grey wolves, but, as their name implies, they have a much redder coat, which looks rather more like that of a typical coyote. Not only that, but they're roughly half way in size between a grey wolf and a coyote, overlapping both large coyotes and small wolves by a considerable margin. And that's where the problem comes from.

You see, we know that wolves and coyotes can cross-breed to produce fertile offspring. Granted, they don't particularly like to do it, and it doesn't always work even we try it using artificial insemination; this, after all, why they're considered different species. But they can, and it does sometimes happen even in the wild. So, given that red wolves look like a cross between a grey wolf and a coyote... how do we know that isn't exactly what they are?

The red wolf was first identified as a distinct species in 1791, under the name Lupus niger.  (Which, oddly, means "black wolf"). This, you will note, is actually before the coyote was named! However, this early description is no longer considered valid, and, by the time the animal received its current name, in Audubon & Bachman's 1851 work Quadrupeds of North America, it was thought to be a subspecies of the regular, grey wolf. A little redder and smaller than the average, to be sure, but subspecies are, after all, supposed to vary in appearance. It was promoted to full species status in 1905, a claim backed up in the '30s, dismissed in the '60s, and backed up again in the '70s. But it can only be a species if it is, in fact, a distinct sort of animal, rather than "just" a wild hybrid.

The first suggestion that it might be a hybrid seems to have been made in 1970, apparently on the basis of physical appearance alone. But, now that we have advanced genetics, shouldn't we be able to answer the question definitively? The first attempt to do exactly that was made in 1991, examining red wolf mitochondrial DNA, and concluding that it matched that of coyotes, and thus that red wolves are, indeed, descendants of some cross between a male grey wolf and a female coyote. But the accuracy of that interpretation was questioned almost immediately, and the debate isn't done yet.

Arguments have swung back and forth over the years since. Certainly red wolves do have a lot in common, genetically, with coyotes. But it could be that they're just really closely related; the two species may have separated less than 0.3 million years ago. Or it could be that the animals we have now are often red wolf/coyote hybrids, but that actual pure red wolves do (or at least, did once) also exist. Generally speaking, the "the red wolf is a species" argument seems to be the more popular at the moment, but it's by no means universally accepted.

Part of the reason that this is so difficult to answer - and, ironically, the reason why such an answer is so important - is that red wolves survive in such terribly small numbers. Once, they inhabited much of the southern and eastern US, from Texas to Virginia, and maybe even as far as Pennsylvania and Ontario. That, however, was before Europeans arrived, and the numbers of red wolves declined drastically over the following centuries. By the 1960s, all that remained were a few animals in the southeastern corner of Texas and the southern swamps of Louisiana. Sightings became increasingly rare, and, some time around 1980, even that population had faded to nothing: the red wolf, whatever it was, was extinct.

Or, at least it was in the wild. Animals did still exist in zoos, and efforts were already underway to restore the species to the wild. While there were a number of other attempts, the only long-lasting success began in 1987, in North Carolina. Today, the only red wolves alive in the wild are in and around the Alligator River National Wildlife Refuge in the east of that state. As of the latest estimate, conducted in 2010, that population numbers a little over a hundred animals, with slightly more still in captivity. The population seems to be increasing, but only slowly, and with such a perilously low population, the red wolf remains critically endangered.

Their existence in captivity means that we do know a fair amount about red wolf biology... their almost total absence anywhere else means that we know a lot less about their behaviour in the wild. Before their re-introduction in North Carolina, they were last seen alive in warm swamplands close to the Gulf of Mexico, but it's unlikely that this was their preferred habitat, rather than simply the last place they could hide. Most likely, given their apparently large range in pre-Columbian times, they were generalists, able, like grey wolves, to inhabit many different types of terrain.

We don't really know what they ate, either. In Texas, they used to eat coypu and swamp rats. In North Carolina, they feed on deer, raccoons, and rabbits. So, again, they're probably adaptable, as both grey wolves and coyotes are, but all we know is that they eat what they can find around them. They live in packs, which seem structured rather like those of coyotes, but, when the population is so low and the potential land area to live in so restricted, it's harder to say how big those packs would be naturally, or how far they'd roam.

If we're right about them being a separate species then they won't normally breed with coyotes. But the situation is hardly normal any more, and the primary threat to their continued existence is cross-breeding with coyotes, and the risk that, if they weren't hybrids before, the only ones left soon will be... before vanishing altogether into the coyote gene pool. Even in the captive populations, where we can be reasonably sure that that isn't happening, litter sizes are decreasing as those left become increasingly inbred.

Fortunately, though, conservation efforts to rescue the red wolf from the brink of oblivion are ongoing, and seem to be progressing as well as could be expected. It's safe to say that they will never regain their former glory, roaming across a third of the continent, but at least they have a chance at continued survival.

[Photos by Mario Massone, from Wikimedia Commons, and B. Bartel of the US Fish & Wildlife Service]

1 comment:

  1. I am a wolf advocate and this blog post is so refreshingly honest in light of the radical eradication of wolves and coyotes worldwide. I look forward to your every post, as I learn so much that is useful in my quest to understand the kingdom of Animalia. Thank you for sharing your knowledge with a world on the brink of losing so many species.