Wolves, Foxes, and Food

Large scary predators are, by their nature, rare. There simply can't be too many of them, or they would run out of food to eat, something typified by the trophic pyramid often seen in biology textbooks: plants are eaten by herbivores are eaten by carnivores are eaten by bigger carnivores, with each step necessarily having a smaller total mass. The reality is, of course, somewhat more complex than this simple chain would suggest, most obviously because it ignores omnivores and decomposition.

But the basic idea holds, and apex predators - those that are large enough that nothing else normally eats them - exist in much smaller numbers than herbivores or smaller carnivores. This means that, relative to their numbers, they have a disproportionate effect on the ecosystem within which they live. Take away the apex predators and, even though there weren't very many of them to begin with, you will radically change the local ecology.

And, because they are relatively few in number, apex predators tend to be especially vulnerable to being wiped out. That's even assuming that humans don't focus on them deliberately out of fear, whether for their own lives or for the good of their livestock. Globally, apex predators are declining. (On this blog, we're mostly interested in mammals, but consider, for example, that at least eight of the 23 species of crocodile/alligator are currently thought to be endangered).

We're Up All Day to Get Lucky

One of the key characteristics that's often listed for the behaviour of a mammal species is what time of day it tends to be active. There are four basic options here, of which the most obvious are diurnality and nocturnality. The others are crepuscularity if it's most active around dawn and dusk but not in between, and cathemerality if it really doesn't care - often because it lives underground. But, either way, it's natural to assume that this behaviour is relatively fixed in an animal; either it's nocturnal or it isn't.

In reality, however, it turns out that this can have a lot to do with the circumstances. And, in the modern world, those circumstances are most likely to be shaped by... what else, but humans? 

The issue, of course, is that humans are for the most part diurnal. Which isn't much of a problem for animals that are naturally nocturnal, but can be if they, too, would prefer to be active during the daylight hours. What we see time and time again across the world, and across different mammal species, is that where humans are most likely to encounter wild animals, those animals shift their behaviour towards nocturnality to avoid the stress of meeting us too often.

Wolves at the Campfire

There's an internet meme, which exists in several different variants, that makes a half-serious joke about dog domestication. A typical version shows a picture of a wolf ostensibly heading to a camp of stone age hunters, hoping to get some food, and thinking "what's the worst that could happen?"... followed by a second picture captioned "thousands of years later" and showing an inbred domestic dog dressed in ridiculous knitwear. The second part is an accurate enough description of what thousands of years of domestication and directed breeding have done to at least some dog breeds. 

But what about the first part? That's showing what's probably a common understanding of how wolves originally became domesticated and turned into dogs. Essentially, dogs domesticated themselves, with those wolves that were least wary of humans, due to whatever quirk in their individual personalities, being the ones most likely to get close to them. Over time, there was further selection in this direction, with the friendliest wolves also becoming the most popular/useful to the humans until, eventually, domesticated breeding was able to take over. 

The Dog Family: Wolves, Dogs, and Dingoes

Eurasian wolf

The best known and most familiar of the species in the dog family is surely the grey wolf (Canis lupus). This is not least because it is the one that we happen to have domesticated, and which most of us see just about every day. Even the wild form is so familiar that there are a great many wildlife documentaries and web pages out there that cover the species better than I can in one blog post, and I don't want to go too much over that ground. But nonetheless, for the sake of completeness, at least some sort of overview is needed here.

The term "grey wolf" is the generally accepted one for the species as a whole. While there are other species that are referred to as wolves, this is the one that we generally mean when we say the word "wolf" without qualification. Most other terms, such as "timber wolf", "steppe wolf", and so on, refer either to groups of one or more subspecies, or are simply alternative terms for the same animal. Once being spread throughout almost the entire Northern Hemisphere (albeit to only a limited extent in Africa), it is unsurprising that there are rather a lot of subspecies.

But how many? That's a question of some debate. I have talked before about how difficult it can be, in practice, to separate one species from another; the problem is even worse when you're trying to count subspecies. One scheme, for instance, has as many as 24 subspecies in North America alone, while another, more conservative, scheme recognises just twelve worldwide. There are a great many opinions that lie somewhere in between.

Wolf or Jackal?

This one really is a golden jackal

A species, you may have been told, is a group of animals that can breed with each other, but cannot breed with other species to produce fertile offspring. So wolves and domestic dogs are the same species, because they can interbreed, while horses and donkeys are not, because mules are infertile. There are a lot of problems with this idea, because it turns out that nature isn't really all that neat and tidy. For example, polar bears are quite clearly not the same thing as grizzly bears, but the two can produce fertile offspring - something that is happening increasingly as the polar ice caps melt and the natural habitat of the polar bears shrinks.

Its also not at all obvious how you're supposed to apply this definition to animals that don't reproduce sexually (though that's obviously not a problem with mammals). And what about those cases where two species have separated so recently in the evolutionary past that some individuals can crossbreed, but others can't? The classic example here are the herring gulls and lesser black-backed gulls, where the Siberian populations of these two species can interbreed, but the British ones can't. It really does get messy very quickly.

Even if it wasn't for all this, if we really did use the fertile interbreeding definition, how useful would it be? Well, we would have to accept that polar bears are really just odd-looking brown bears, for a start. But more than that, what about other species? Are we really going to try and cross-breed every plausible combination to see what happens? It can be hard enough to get some animals to breed in captivity at the best of times, making the whole idea completely impractical.

Inevitably, this means you sometimes have to end up applying some common sense, and describing something as a separate species largely because it's useful to do so. So polar bears, for example, are considered a species, because they are different in so many ways from brown bears. At the opposite end of the scale, there are many species that don't generally interbreed, but are so closely related that they look almost exactly the same, making it really hard to tell where one species starts and another ends. A lot of these are mice of various kinds, but it's also true of dogs.

The wolf (Canis lupus) is a very widespread species. Before humans drove it off from many parts of its range, it was found throughout Europe, and in most parts of Asia and North America. Human intervention brought them to Australia, in the form of dingos, and the domestic dog is also considered a subspecies of wolf. They once used to inhabit the southern coast of the Mediterranean, but now wild wolves are completely absent from Africa. Or are they?

The closest living relative of the wolf is the golden jackal (Canis aureus). Golden jackals are found in the Balkans, and across Arabia and southern Asia, but they are also found across northern and eastern Africa as far south as Nigeria. It would seem, therefore, that the golden jackal is more suited to these hot climates than its more northerly cousin, the wolf.

Wolf      Golden     Coyote    Ethiopian
          Jackal                 Wolf
  |          |         |           |
  |          |         |           |
  |          |         |           |         Other
  ------------         -------------        Jackals
       |                     |                 ^
       |                     |                 |
       -----------------------                 |          Dhole
                 |                             |            |
                 |                             |            |
                 -------------------------------            |
                                |                           |
                                |                           |
                                -----------------------------
                                              |
                                              |

Like the wolves, golden jackals are a varied bunch, with several different subspecies recognised. Indeed, one subspecies, found in Egypt, is quite hard to tell apart from a wolf - were it not for the fact that, officially, there are no wolves in Egypt. There had been some dispute in the past as to the exact status of these Egyptian animals, but, more recently, some very wolf-like jackals were also spotted much further south, in Ethiopia. Were they really jackals, as the textbooks said they had to be, or were they something else?

You can't just capture them, breed them with wolves, and see what happens. Not least because we know that wolves can breed with coyotes without any difficulty, and they're certainly a different species, so fertile offspring produced in captivity wouldn't prove anything either way. To see what they really are, we need to look at their genetics. If two groups of animals regularly crossbreed in the wild, their genetics should be very similar, and we have as good a reason as any we can come up with to say that they're really the same species.

So that's what the researchers did. They collected samples of the animals' dung, sequenced their DNA, and compared it with samples taken from jackals in Egypt, with wolves and golden jackals from a range of locations, and, for good measure, from seven other species of the dog family. (Including foxes - when you're doing this sort of test, you need to include something that's sort-of-similar yet manifestly not the same, just to make sure it's working properly).

Of course, they didn't analyse the entire genome, since modern technology isn't up to making that at all routine. Instead, they looked at a particular gene, cytochrome b, which is used as a standard in these sorts of studies. It's presumably not perfect, but with everyone using the same gene, at least it is possible to compare results with those from other workers, and this particular gene has done a good job so far at figuring which mammals are related to which other mammals.

The results showed, firstly, that these Ethiopian jackals were almost identical, genetically, to the ones seen in Egypt. This alone is significant, since it means that this subspecies is found much further south than previously thought. But it also showed that these animals were more closely related to wolves than to other golden jackals. Indeed, in some respects, they were more similar to wolves from places like Canada and Sweden than they were to wolves from the Himalayas.

So, whatever these animals are, they can't possibly be golden jackals. It appears that they diverged from the main group of wolves after the Himalayan wolves did, which means they have to be wolves, too. All the textbooks say there are no wild wolves in Africa, but we now know that there are - at least in Egypt and Ethiopia, where they have been living alongside golden jackals, and looking so similar that few people could tell them apart.

This is exactly the sort of problem that occurs when you have very similar looking species living side by side. Indeed, this sort of finding crops up quite often with mice, with nobody much noticing (or caring, frankly). But even then, is this animal actually a subspecies of wolf, or something else entirely? Just a few years ago, it was argued that Himalayan wolves were themselves a separate species. If that's right, then the Ethiopian animals might well be a species of their own, too - one we didn't previously know about. It's debatable either way, since they do seem to be much closer to northern wolves genetically than we'd expect a new species to be, yet different enough that a blood test will tell them apart.

Does it matter, though? Do we care whether this is a species or a subspecies? Well, funnily, enough, yes it does make quite a difference. Wolves are not an endangered species (and neither are golden jackals), so if these animals are a special sort of wolf, they will get relatively little protection from the various international conventions about such things. But if they're a species, then there's pretty good reason to suppose they might be endangered - there certainly aren't very many of them, and the local farmers do have a habit of killing them to protect their livestock. That's not a problem (from a species conservation perspective) if they're also found elsewhere in the world, but if this is the only place the species is found, then they can get protection under international law.

Considering that we can't come up with a good definition of what a species is, it makes a heck of a lot of difference whether a group of animals is one or not.

[Picture from Wikimedia Commons]