Natural History

I’m currently reading John Lane’s excellent book, Coyote Settles the South. It is an excellent book, and I will be reviewing it here very soon. The whole time I’ve been reading it I thinking about my encounter with the male Eastern coyote I called in back in March.

He’s not exactly the same coyote that Lane is writing about. He’s a coyote of the gray woods, not the subtropical pine forests and river bottoms.

But in some ways, he is the same. He is the same creature that has adjusted to all that Western man can throw at him and thrived.

And he’s thrived at the expense of the wolves that once roamed over the Northeastern US and the South. He’s just the right size to live on a diet of rodents and rabbits but also has the ability to pack up and hunt deer. He can be an omnivore, enjoying wild apples and pears that fall to the ground, almost as much as he would if he came across a winter-killed deer.

The coyote is a survivor. I’ve written on this space several times that the reason he has thrived is because he has been here far longer than the wolves that once harried his kind. Until last week, it was assumed that the coyote split from the wolf some 1 million years ago. This million year split has been used for virtually every study that has examined the relationships between different populations or species in the genus Canis. It is used to set the molecular clock so that we can figure out when wolves and dogs split and perhaps give us some idea as to when dogs may have been domesticated.

This assumption has been directly challenged in a new study that was released in Science Advances last week. The paper examined full genome sequences of several different canids, and it can be argued that it pretty much ended the debate as to whether the red wolf and Eastern wolf are species. They aren’t. Instead, they are the result of hybridization between wolves and coyotes. Most of the media attention has paid attention to this discovery in the study.

It’s the most important practical implications, because the US Fish and Wildlife Service delisted the gray or Holarctic wolf in most of the Eastern, Southern, and Midwestern states in favor of protecting the Eastern and red wolves. Red wolves are called Canis rufus, and  Eastern wolf is Canis lycaon. With them being recognized as hybrids, this greatly complicates the issue of how to conserve them under the Endangered Species Act, which, as its name suggests, is meant to conserve actual species and not hybrids between species.

The authors of the study feel that these hybrid populations are still worth conserving, largely because the red wolf contains the last reservoir of genes belonging to the now extinct wolves of the Southeast.

But in order to make this work, we’re probably going to have to rewrite the Endangered Species Act, and that is not going to happen any time soon.

However, the finding in the study that is worth discussing more is that not only showed that red and Eastern wolves were not some relict ancient species of wolf. It is the finding that coyotes and wolves split only 50,000 years ago.

Using a simple isolation model and a summary likelihood approach, we estimated a Eurasian gray wolf–coyote divergence time of T = 0.38 N generations (95% confidence interval, 0.376 to 0.386 N), where N is the effective population size. If we assume a generation time of 3 years, and an effective population size of 45,000 (24, 25), then this corresponds to a divergence time of 50.8 to 52.1 thousand years ago (ka), roughly the same as previous estimates of the divergence time of extant gray wolves.

This finding means that the studies that use that 1 million year divergence time to set the molecular clock for all those dog domestication studies need to be reworked. This is going to have some effect on how we think about dog domestication, and although the domestication dates have been moved back in recent years, the actual split between dogs and wolves is likely to be much later than when we see the first signs of domestication in subfossil canids.

That’s one important finding that comes from this discovery that wolves and coyotes are much more closely related.

The other is that yes, it did pretty much end Canis rufus and Canis lycaon as actual species, but it probably also ends the validity of Canis latrans as a valid species. Coyotes could be classified as a subspecies of wolf. Indeed, they are much more closely related to wolves than Old World red foxes are to New World red foxes, which split 4oo,ooo years ago. And there is still some debate as to whether these two foxes are distinct species, because we’ve traditionally classified them as a single species. Plus, if we start splitting them into two species, we’re likely to find the same thing exists with least weasels living in the Old and New World. And the same thing with stoats.

And then it’s not long we’re fighting over the house mouse species complex.

But if we’re going to lump red foxes, it’s pretty hard not to lump coyotes and wolves. It is true that wolves normally kill coyotes in their territory, but it also found that wolves in Alsaska and Yellowstone, wolves that were thought to be entirely free of any New World ancestry, also had some coyote genes.

So the coyote, like the extinct Honshu wolf and the current Arabian wolf, could be correctly thought of a small subspecies of wolf. We know from paleontology that in both North America and Eurasia there were various forms of canid that varied from jackal-like to wolf-like, and although we know the jackal-like form is the earliest form, these two types have ebbed and flowed across Eurasia and North America. We’ve assumed that the jackal-like forms gave became the coyote and the larger wolf-like forms have become the gray, red, and dire wolves.

But what we’re looking at now is the coyote isn’t the ancient species we thought it was. It’s very likely that some ancestral wolf population came into North America, and instead assuming the pack-hunting behavior of Eurasian wolves, it tended toward the behavior of a golden jackal. When this ancient wolf walked into North America, it would have found that the pack-hunting niche was already occupied by dire wolves. There were many other large predators around as well, and evolving to the jackal-like niche would have made a lot more sense in evolutionary terms.

This is what the coyote is.

The pack-hunting modern wolf came into the continent and took it by storm, and the coyote exchanged genes with it. They lived together as sort of species-like populations in the West, but when wolves became rare from persecution following European settlement, the coyote and wolf began to exchange genes much more.

So with one study using complete genomes, the entire taxonomy of North American Canis is truly blown asunder.

And the implications for dog domestication studies and for the practical application of the Endangered Species Act could not be any more consequential.

Very rarely do you get studies like this one.

It changes so much, and the question about what a coyote is has become unusually unsettling but also oddly amazing.

I will never think of a coyote the same way.

The mystery is even more mysterious.