African wild dogs do have front dewclaws

 

African wild dogs are rather unique among canids in that they naturally possess only four digits on their front paws. The dewclaws are missing.

Or are they?

In a study published in PeerJ in September, researchers report that they have discovered these dewclaws. They exist as vestigial metacarpals that are deep within the skin of their front wrists.

The reduction of the dewclaws (or "first digit") has coincided with shift in the muscles around the front feet. This shift gives African wild dogs greater awareness of their feet and body position when running.

The African wild dog and the dhole are specialists in a type of hunting that involves running down ungulate prey over a long distance chase.  Wolves do a similar type of hunting behavior, but they also adjust their behavior to ambush small prey. They are much more of a generalist predator than dholes and African wild dogs are.

All extant canids belong to the subfamily Caninae. this subfamily first appeared in the fossil record about 34 million years ago with Leptocyon, a very small fox-like dog.  The other two subfamilies are now extinct. One was the Hesperocyoninae, the most basal lineage of all dogs. They looked more or less like someone had hybridized a gray fox with a ring-tail. The other lineage was the Borophoginae which included a whole host of different forms and shapes. The lineage never produced a specialized running dog of any kind, even though it produced the largest dog species ever recorded, Epicyon.

The larger Borophaginae were probably ambush predators. Epicyon is thought to have pounced on its prey in much the same way that foxes do. The difference is that  Epicyon hunted big prey. These large ambush predators existed for nearly 15 million years, only going extinct 6 million years ago.

The Hesperocyoninae were outcompeted by the growing Borphagine radiation around 16 million years ago.  The modern ancestors of Caninae remained smaller and adopted a more cursorial niche, a niche they would exploit when large Felids began colonizing North America. Cats are better adapted to hunting in the ambush style, and they simply outcompeted the Borophagine dogs.

With the extinction of that branch of Canidae, the extant modern lineage of dogs could exploit the cursorial hunter niche. All extant species do have adaptations for running, but these adaptation are the least derived in gray foxes and raccoon dogs, which both still climb trees, and most derived in African wild dogs and (to lesser extent) in dholes.

Developing a running foot from a climber's paw is a difficult feet of evolution. Both odd-toed and even-toed ungulates have a lot longer history to adapt their feet for this purpose

But in the case of the African wild dog, these adaptations are moving along.

Maybe in another ten million years, this species will have hooves!

Gray fox numbers on the decline in the Midwest

Long-time readers of my blog know that I have a long fascination with the gray fox (Urocyon cinereoargenteus). It is the most primitive of extant dog species, which apparently diverged from the rest of the dog family between 10 and 12 million years ago.  It might represent several cryptic species, though only the insular dwarf form from the channel islands is currently recognized as a distinct taxon. 

When I lived back in the woods in West Virginia, gray foxes were common trail camera captures. The video embedded in this post one of my best captures of the species. They were quite common in the backwoods of West Virginia, which has extensive, dense forests that are quite inaccessible to humans. These foxes prefer to live deep in the thicket, where they can always shoot up a tree if they ever feel threatened.

I now live in Northeast Ohio, and I have seen foxes here and in adjacent Pennsylvania. Every single one has been a red.

It turns out that gray fox numbers have greatly decreased in much of the Midwest, and  now researchers are trying to figure out why. 

A simplistic answer is that coyotes are killing them all. Coyote numbers are on the increase all over the Eastern and Midwestern US. But if coyotes were killing every fox they encountered, the numbers of red fox would have much more dramatic decline. Red foxes cannot climb trees, and they tend to hang out in areas where coyotes would likely encounter them more often, especially in agricultural areas.

But red fox numbers have not declined.

One possibility is that increased competition from growing raccoon numbers could have led to a reduction in gray fox numbers. Raccoons are not hunted or trapped nearly as intensively as they once were, and raccoons have a very similar diet to the gray fox, which is quite omnivorous.

Further, raccoons do carry canine distemper, a disease that is quite devastatingly fatal to gray foxes.

Now, coyotes carry distemper, and they also would compete for prey resources on which gray foxes rely.

So it is possible that the issue with coyotes and gray foxes comes from an indirect conflict, rather than outright predation.

The decline of the gray fox in the Midwest has wildlife researchers quite vexed. This problem coincides with a range expansion of the gray fox in the Northeast, a region that is also full of raccoons and coyotes.  Indeed, a New England gray fox crossed the border in New Brunswick, entering the Maritimes of Canada for the first time in centuries. 

So if the foxes are thriving in the Northeast and even expanding their range, it is unlikely that simple adversarial relations between red foxes and other carnivora are the answer.

This question is one that must be teased out in the scientific literature, but if gray foxes are going to be part of the native fauna of the region, it must be answered.

The Hunting Symbiosis Model of Dog Domestication

 

A lot of discussion about dog domestication is a debate between the scavenger vs. the hunting-symbiosis model.

  I don't think the scavenging model is well-supported from the empirical reality of when it appears dogs where domesticated.  Virtually all genetic data supports a domestication of the dog thousands of years before humans engaged in agriculture. Agricultural society currently has created a surplus where things like coyotes, raccoons, red foxes, and even some wolf populations engage in widespread scavenging of our waste. Hunter-gatherers simply didn't have enough food waste to feed scavenging wolves that could somehow evolve into dogs.

There have been some attempts in the past month to make this model viable again.  A paper was recently published in Nature that points out that humans have a very hard time digesting excess protein from their kills. Humans require fat from meat to power our freakishly large brains, but excess protein is a real problem for us. The authors contend that wolves would have scavenged the lean cuts of meat, and humans would have eaten the fattier ones.

Thus, because humans and wolves would have preferred different parts of the animal, humans would have created a glut of waste in lean meat, which the wolves would have devoured. 

I think this is still a bit of stretch, and I think it points more toward the hunting-symbiosis model of dog domestication. 

The fact that humans and wolves would have preferred different parts of the animal shows how this symbiosis could have been maintained much more easily than the fanciful notion that people were leaving garbage heaps of lean meat cuts.

I think the story of dog domestication began with a long-term relationship between wolves and people. I think it may have gone something like this: 

Wolves often test ungulate prey. Generally if prey is healthy, it stands and faces the wolves. If it is not healthy, it runs, and the wolves run it down and kill it. 

Healthy animals are likely to have good amounts of fat on them, which hunting humans would need to power their brains, but healthy animals are by definition hard to kill.

Wolves harrying and testing quarry, which do two things for these hunters. When the quarry stands to face the wolves, it becomes distracted and more stationary-- and much easier to hit with a thrown spear. The health of the animal that would give it it the guts to stand and face the wolves would make it more vulnerable. 

This way of hunting with wolves is suggested in Pat Shipman's The Invaders.  She contends that European hunters would use wolves to bay up mammoths, distracting them them the human approach and making them easier to kill. 

This hunting technique is not at all dissimilar to how Scandinavian hunters use elkhounds. The dogs distract the large cervids (better known to North Americans as moose). The distracted and mostly stationary moose is then more easily taken with a rifle. 

That humans have a hard time digesting and metabolizing lean protein actually points more towards the hunting symbiosis model for dog domestication, a idea explored more thoroughly in Pierotti and Fogg's First Domestication. 

Wolves and ravens have been observed cooperatively hunting together. The ravens will search from the sky, looking for a weakened moose or caribou. The wolves then kill the weakened animal, and both the wolves and ravens get a chance at the kill.

It makes sense that wolves, which had not yet undergone the brutal selection that agricultural and industrial man performed upon the species in more recent centuries, would have been more than willing to engage humans in the same way. And humans would have found this method of hunting was a great way to get fatty meat very easily.

So it makes sense that humans and wolves could have worked together, perhaps for tens of thousands of years, until there was ever a discernable creature that we might call a dog.

The antiquity of dogs means we are forced to consider that cooperative hunting played a vital role in their evolution and eventual domestication.

To do otherwise is engage in a sort of logical gymnastics that makes one look quite a bit foolish.

So it began with bay dogs in a world of ice and snow.

The Last Glacial Maximum Played a Major Role in Dog Domestication.

Indigenous siberian with a laika. This is not a Native American with a Native American dog. However, a new study reveals that Siberia could be the point of origin for the domestic dog. It also the first dogs
 in the Americas came with Siberian hunter-gatherers 15,000 years ago.
 

A new study  released in PNAS today revealed that dogs were domesticated around 23,000 years ago in Siberia. This study, which looked at ancient DNA from dogs and humans from Eurasia and North America, revealed that Siberia is likely the point of origin for dog domestication. Further, the authors were able to demonstrate that ancient North America dogs derive from this Siberian population, entering North America around 15,000 years ago, which is roughly the same time that the first humans entered the continent.

The authors contend that 23,000 years ago roughly coincides with the last glacial maximum, which could have put increased pressure on humans and the wolves that led to dogs to form the relationships that eventually gave rise to domestic dogs. 

The findings of this study are pretty unique, because they come from a pretty well-designed analysis of ancient dog remains. And there is comparison to human dispersal in the late Pleistocene.

A 2013 study in PLOS One revealed that the remains of a 33,000-year-old canid from a cave in the Altai mountains was a dog, and this creature was closely related to the ancient American domestic dogs.

These findings seem to be somewhat contradictory, and I think we need to be careful in assuming that the origin for the domestic dog has somehow been find at long last.

It is possible that the authors are picking up on in the new study is the role the last glacial maximum played in creating a distinct dog lineage.

Mark Derr in his book How the Dog Became the Dog posits that the last glacial maximum was instrumental in creating the distinct "dog" morphology in domesticated wolves, but it is very possible- and it is pretty likely-- that ancient humans had a relationship with wolves going back deeper than the 23,000 years posited in the study.

Indeed, the authors of the new study point out that the last glacial maximum could have isolated these wolves from other wolves, allowing for a more rigorous selection for great symbiosis with humans.

This idea is quite intriguing, because it is very likely that human and wolf relationships in Eurasia go much deeper than the ones that ultimately lead to dog domestication as we know it now. For example, we have several examples of ancient European "dogs" that date to around 31,000 years ago, including one in what is now the Czech Republic that was apparently interred with a bone in its mouth.

So it is very possible that the lineage of wolves that became modern dog lineages was finally made distinct from other gray wolves 23,000 years ago, but we likely have several periods of domestication and semi-domestication that stretch across Eurasia for thousands of years before the last glacial maximum. Some of these domesticated and semi-domesticated wolves could have rejoined the wild population, and wild genes could always be filtering in. 

The truth of the matter is that after reading Pierotti and Fogg's wonderful book on dog domestication, one wonders if we will ever know when dogs became distinct from wolves. But it would be reasonable that the last glacial maximum could have played a role in that transition.

The Dire Wolf was a wolf in parallel

 

Mauricio Anton's depiction of gray wolves fighting dire wolves over a bison kill. This reconstruction is based upon the new dire wolf genome paper that reveals that many of North America's wolf-like canids were not particularly closely related gray wolves and coyotes.

Dire wolves have captured the public imagination for some time now. Game of Thrones fans know them well, and our popular understanding of them is that they were like very big gray wolves.  Game of Thrones embellished their size, but they were larger on average than a typical Northwestern gray wolf, the subspecies that ranges through the Pacific Northwest, most of Alaska, and much of the Northern Rockies.

My understanding was that a dire wolf was very much like a very big gray wolf that had special adaptations to hunting megafauna. It was very similar to the Beringian gray wolf, an extinct ecomorph of gray wolf that ranged from Alaska to Wyoming  It, too, was adapted for hunting very large prey.

Paleontologist had developed phylogeny of the dire wolf based upon comparative morphology.  Wang and Tedford contended that the dire wolf derived from a large Pliocene Chinese "wolf" (Canis chihliensis). Their work contends that this Chinese canid was the common ancestor of the gray wolf and dire wolf, a claim for which I have always been skeptical. European paleontologists have shown rather convincingly that ancestor of the gray wolf was the Mosbach wolf.

What I was always hoping for was that someone would be able to extract DNA from dire wolves and maybe answer my skepticism.

Even with my general view that the Mosbach wolf was the ancestor of the gray wolf, I still accepted that there was a North American wolf radiation that paralleled the evolution of the gray wolf in Eurasia.

But every time I would look more closely at the paleontology literature, I would be more confused. For example, one species posited in the dire wolf's lineage was Edward's wolf (Canis edwardii). This animal has been suggested as an ancestor the putative "red wolf," and Dan Flores made a big deal out it being the ancestor of the coyote in Coyote America, even though it was closer to the red wolf in size. This literature gets somewhat confusing because Edward's wolf is sometimes listed as Canis priscolatrans, but they are now generally regarded as the same species.

None of this makes much sense, especially with the new literature clearly showing a much closer genetic relationship between the coyote and gray wolf. If this closer relationship is true, the coyote is not an ancient New World canid. If that more recent origins date is accurate, the coyote is actually a form of gray wolf in much the same way that the domestic dog is.

So I have many questions about North America's wolf-like canids. I have found the paleontology literature not particularly enlightening, because the genomic data almost entirely contradicts its theses.

But a few days ago, a paper was published in Nature that vindicated my skepticism.  Genomes were sequenced from the subfossil remains of five dire wolves. They then compared that data to extant wolf-like canids using a Bayesian analysis called an MCMCtree. 

The authors discovered that dire wolves were not closely related to extant wolves or coyotes. Instead, they diverged 5.7 million years ago  They turn out to be most closely related to the endemic African jackals, now often classified in the genus Lupullela rather than Canis. 

This study has profound implications about wolf evolution. It clearly shows that coyotes originated from Old World ancestors, and they are not direct descendants of Canis lepophagus, the first Canis species that appeared about 5 million years ago in North America. It is also is also not descended from Canis edwardii/Canis priscolatrans.

 

This study suggests that a whole lineage of parallel wolves existed in North America that were quite distinct from modern ones. Canis edwardii might belong to this lineage, and Canis armbrusteri, the ancestor the dire wolf, most definitely does. 

In the same way that many experts are now using Lupullela as the genus for the endemic African jackals, the researchers associated with this paper have suggested that the dire wolf be called Aenocyon dirus, the "terrible wolf." Armbruster's wolf should also be reclassified in this genus, and it is possible that Edward's wolf will be too.

Further, if these dates of divergence hold, the common ancestor of the dire wolf and North American endemic wolf lineages would be somewhere in the genus Eucyon, which existed very near the divergence between wolf-like canids and the "South American clade" of canids, the Cerdocyoninae. So this famous reconstruction depicting the dire wolf as a robust bush dog might not be as far-fetched.

Two years ago, I wrote that some of our assumptions about dire wolves might be wrong, and I am honestly surprised that this layman produced some hypotheses that were later shown to be correct. Full disclosure: I never spoke a word to any of these researchers, nor did they contact me. I am not such a narcissist to assume they ever read what I write. I am not a scientist, but I am one of their stenographers and exponents.

I even introduced this whole idea through an April Fool's prank. I had no idea that my prank would actually turn out to be a major finding in a paper almost four years later. 

So, yeah, there is that.

I should note that the authors used a Bayesian statistical approach for the dire wolf genome study, which is a methodology that includes probability models that are based upon previous research, The coyote-gray wolf genome paper that I often refer to used a frequentist methodology, which does not set up such parameters. This is why the dire wolf paper shows a 1.1 million year divergence between the coyote and gray wolf,, and the other paper shows a 51,000 year divergence. I would like to see this paper recalibrated using either a frequentist analysis or a Bayesian analysis that includes this as one of the parameters. The dates will be quite a bit different, but they still show this extinct lineage of North American wolves.

The exact phylogeny and taxonomy of wolf-like canids is not entirely clear, but the relationships are coming more into focus. This paper is as much a revelation about the evolution of these creatures as the paper discovering more recent origins between the coyote and gray wolf.

The researchers of this dire wolf paper discovered no evidence of gene flow between the dire wolf and the gray wolf and coyote, which both apparently colonized North America from Eurasia.  It may have lacked the behavioral and morphological flexibility that allows gray wolves and coyotes to thrive in constantly changing environments. Further, it might have susceptible to diseases that proliferated from growing populations of gray wolves and coyotes.

Popular press coverage of the new placement of the dire wolf within the wolf evolution story often points out how surprised the researchers were by the discovery. One researcher even thought the dire wolf would come up as a subspecies of the gray wolf, a possibility that certainly made some sense. 

Because canids have a tendency toward morphological plasticity and convergent evolution, our ability to determine the taxonomy and phylogeny of these species based upon morphology will always be limited. This is why the paleontology got so much of this wrong.

Sometimes what you think you see really isn't there at the molecular level. 

 

57,000-year-old wolf pup discovered in the Yukon

 

In 2016, the mummified remains of a wolf pup were found in melting permafrost in the Yukon. The remains were very complete, but it seemed that they likely came from a very ancient form of wolf.

A few weeks ago, a detailed analysis of this wolf pup's molecular biology was published in Current Biology.  Radiocarbon dating suggested that the pup, which was estimated to have been between six and seven weeks old when she died, lived greater than 50,000 years ago. More in depth isotopic analysis revealed her exact age to be between 56,000 and 57,000 years old.

Ancient mitochondrial DNA was extracted and compared to ancient and modern gray wolf remains. She was found to be basal to all extant wolves and had a strong relationship to Pleistocene Russian and Beringian wolves, which would have been expected from her location 

The researchers were able to determine through isotopic analysis that her diet and that of her mother from which she had suckled most of her life came from marine sources.

So this ancient wolf was living very much like the now famous wolves of coastal British Columbia that also live almost exclusively on fish, shellfish, and marine mammals.  A great deal of speculation exists about these wolves potentially evolving into a marine mammal, but the discovery that this ancient wolf and the population of which she was a part shows that wolves have lived on very similar resources before. The wolves of the British Columbia coast are not the first of their kind to live this way. They have merely adopted it in parallel from a now extinct population..

One point of interest for me is the age of the wolf is estimated to have been between 56,000 and 57,000 years ago. The most recent analysis of the gray wolf and coyote genomes reveals that coyotes split from gray wolves around 50,000 years ago, which might suggest that this animal might also be basal to coyotes.

The researchers looked at only her mitochondrial DNA, and they did not compare her to coyotes. Coyotes have an unusual mitochondrial DNA heritage, which might have come from an introgression from a dhole-like ancestor.

This discovery raises many interesting questions. 

It is not impossible for full genomes to be extracted from such old specimens. A 700,000-year-old horse had its full genome sequenced, and the results had amazing implications for our understanding of horse evolution. 

This wolf pup could very well have that same potential. I hope that more work is performed on its molecular evolution. It could very well tell us a very interesting story. 

New Platform

 

Because of my issues with the new Wordpress editor, I have moved over to this platform.

I have never much liked Blogger's system, but its editor is way more user-friendly than the one that Wordpress has developed.

The last few months have been rather rough. We have had to euthanize Drake, the male greyhound, because of bone cancer, and I have not been feeling like writing all that much.

So I am coming back.  Slowly but surely.

And we will see new things once again.