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Archive for the ‘wolves’ Category

Quite a chase!

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Yep. This has to have been the first documentary about wolves I ever watched. Jim Brandenburg and David Mech hanging out with a wolf pack from a population that has never experienced persecution:

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dire-wolf-baculum

Dire wolves are one of those creatures from the past that has captured the public imagination. They are conventionally dreamed of as being massive wolves, and Hollywood has created fictional ones the size of horses.

The truth of the matter is they were only slightly larger than the largest of modern North American wolves.

We know that they were closely related to modern wolves, but their exact position in the wolf family tree is still a bit contested.  The two species are close enough in appearance that it often takes a specialist to figure out whether one is looking at the skeletal remains dire or modern wolf the measurement of the skull features and limb proportions.

One feature, though, that is diagnostic of the dire wolf is its  robust and “perky” baculum.

If you don’t know what a baculum is, that’s because you’re human. In virtually ever other species, the males have a “penis bone” or os penis.  Where I grew up in West Virginia, it was not unusual for men to wear a raccoon’s baculum as talisman of both one’s virility and redneck bona fides.

The dire wolf is one of those ancient animals for which we have a lot of skeletal remains to examine.  In the famous La Brea Tar Pits, where the remains of over a million Pleistocene creatures have been found, dire wolves are the most common species to have been recovered.

The tar pits were a death trap for all sort of large herbivorous mammals, and when they became stuck in the natural asphalt tar, they were easy pickings for scavengers.  Dire wolves came to the tar pits to eat, but many, many of them died. Over 200,000 of them have been taken out of the site.

With such a big sample of dire wolf skeletal remains, paleontologists have been able to figure out quite a bit about their growth patterns, but of particular interest are the bacula of the male dire wolves.  They are shaped not the bacula of any extant canid. They are curved and robust, and when compared to modern wolves of the roughly the same size, they are 44 percent longer.

That is a unusual find, and it suggests something about dire wolf behavior that isn’t true of modern wolves.

Modern wolves generally reproduce through a mated pair. In most wolf packs living in most situations in the wild, only a single pair in a pack gets to mate and produce pups. Other wolves in the pack might mate, but their pups will either be killed or abandoned.

This doesn’t happen every time. If there is abundant prey, these young females are sometimes allowed to raise their pups alongside their mother’s litter.

But in most cases, they don’t get to raise pups.

Modern wolves spend a lot of energy making sure that the mated pair, who are usually parents of the other wolves in the pack, get to mate and get to mate with each other.  The other females in the pack might become pregnant, but they will be attacked if they try to mate with the main breeding male.  The only way they ever get pregnant is by wandering interlopers who haven’t yet formed a pair bond with a female.

During the mating season is when young wolves typically leave their parents’ pack.  They typically don’t have any mating opportunities, and the constant bickering wears on them.

The big and strangely shaped bacula of dire wolves suggests they might not have been quite like modern wolves.  These bacula are suggestive that dire wolves were “better endowed” than modern wolves, and larger genitalia is usually associated with a less physically competitive reproductive strategy.

This phenomenon is well-known in primates. Generally, if a monkey or ape has bigger testes or penis, there is going to be less physical confrontation when it comes to mating.

The competition for well-endowed monkeys is how much semen a male can produce and how far up in the female he can penetrate it. If you can produce more semen and get it deeper into the female’s reproductive tract, then you’re more likely to pass on your genes.

In less-endowed species, there is much more physical confrontation to get one’s genes passed on.

My guess is that this applied to dire wolves. They may not have even had a proper pair-bonding system, and a dire wolf bitch may have mated with many partners in much the same way female domestic dogs do.  The male dire wolves may have had very little competition for mating. They just mated and got along with each other.

It would have been an asset in a dire wolf pack for males to have gotten along with each other. More peace in a dire wolf pack means that more wolves remain in the pack for a longer period of time, and that means they would have had larger packs that would have been much more capable at hunting large prey. They also would have been better able to run off short-faced bears from their kills and to compete with Smilodons and American lions.

It’s likely that the intense competition between huge carnivorans during the dire wolf’s reign forced them into a more cooperative breeding and pack structure.

Again, no scientist has ever seen a dire wolf or observed their pack behavior, but they had this weird adaptation that sort of points to a more peaceful pack existence than exists in the modern species.

My guess is that dire wolves traveled in massive swarms, much like those seen in dholes of today. They were ruthless scavengers and dogged hunters.

When mating tame came, they bred like village dogs. Males would bunch up around a bitch in heat and each would mate with her. There would be no pair bond between the male and female.

The competition was in the semen and the implantation thereof.

 

 

 

 

 

 

 

 

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This is now playing on Netflix:

These wolves really do remind me of coyotes, right down to their consumption of fruit when it’s available.

 

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brush wolf

It cannot be overstated how much the discovery that coyotes are not as distantly related to wolves as we believed ultimately questions our entire understanding of the evolution of the Canis species.

The traditional understanding Canis species evolved from some form of Eucyon dog some six million years ago. Wang and Tedford, who wrote the most important book on the paleontology of the dog family, believe this was Eucyon davisi, which was the first of its genus to enter Eurasia. The genus Eucyon is where the common ancestor of the Canis dogs (including Lycaon and Cuon) and the South American wild dogs would be located. Eucyon dogs were small. Imagine them as being something like a black-backed jackal or a Hoary fox rather than a coyote.

Then, 5 million years later in the Southwestern US and northern Mexico, a coyote-like Canis evolved, which was called Canis lepophagus. This animal is sometimes considered the common ancestor of wolves and coyotes. It may be, but considering how close we now know wolves and coyotes are now, it’s not the most recent common ancestor. Canis lepophagus did migrate into Eurasia, where it either founded or is identical to Canis arnensis.

In Eurasia, several smaller jackal-to-coyote forms evolved. One of these was Canis estruscus,  which then evolved into Canis mosbachensis (which is called Canis variabilis in China).

Ron Nowak believed the red wolf was an offshoot of this wolf that wound up colonizing North America and then becoming isolated from the rest of Canis mobachensis when the ice sheets expanded. There was also a competing view that the red wolf was actually a remnant version of Canis edwardii or Canis priscolatrans (which were probably the same animal). This animal was roughly the size of a red wolf, but Nowak rejected it as a red wolf ancestor because it lived too early for what he thought were red wolf fossils.

The Eurasian wolf species evolved mosbachensis-variabilis, but the two forms of wolf shared habitat and likely exchanged genes, making it very difficult

The coyote’s evolution was never clear. It was thought to have evolved out of Canis lepophagus. It was thought that lepophagus evolved into edwardii, and then it began to become more gracile and smaller, eventually becoming the now coyote.  It’s now pretty clear that it evolved out of the Eurasian Canis lupus and not these endemic North American “wolves.”

It either evolved from the modern wolf, which evolved into roughly its current form 800,000 years ago, or it came from a late surviving mosbachensis-type wolves that were regularly crossing with modern wolves before they came into this continent. Maybe the remains that Nowak had been considering “red wolves,” were actually these ancestral wolves that were evolving into the modern coyote.

Maybe when this wave of wolves came back across from Eurasia, perhaps 50,000-100,000 years ago, it came into a world already dominated by a dire wolves, which already occupied the niche for large, pack hunting canids and this wave of Canis lupus evolved as the American jackal.  After all, the bobcat is just a diminutive Eurasian lynx that found itself in a very similar position when it came into this continent, and it evolved to be a smaller animal that generally hunts smaller quarry than its larger ancestor. Of course, the modern bobcat didn’t reach its current form until about 20,000 years ago, but it still was forced to adapt to a slightly different niche than its Eurasian ancestor.

In literature on the paleontology of Canis, there is a heated debate as to how these animals all fit. The conventional view is that the wolf evolved from Canis mosbachensis/variabilis through Canis etruscus, which may be the same thing as Canis edwardii/ Canis priscolatrans. Wang and Tedford contend that the coyote and wolf split from Eucyon.  The modern wolf evolved from Canis chihliensis, which was a large wolf-like canid. It spread into North America to found Canis armbrusteri, which then evolved into the dire wolf (Canis dirus) in North America and Canis gezi and Canis nehringi in South America.  In the Old World, another offshoot of chihliensis gave rise to Canis falconeri, which the supposedly gave rise to the Xencyon, which is supposed ancestor of the dhole and African wild dog. Another view holds that the Armbruster’s wolf (C armbrusteri) is descended from edwardii/priscolatrans (which may be the same as etruscus). This lineage then gave rise to the dire wolf and the two sister species in South America, thus descending solely from North America wolves.

All of these ideas come from paleontology, and they pretty much are done without looking very deeply into the studies that are examining the DNA of these species. It is pretty obvious from that literature that the notion that coyotes and wolves split at the time of the Eucyon ancestor is quite wrong. For that hypothesis to work, African of  wild dogs and dholes would have to be genetically closer to wolves than coyotes and golden jackals are. They aren’t.

But if the genome-wide analysis shows that coyotes are so much more closely related to wolves is true, then all these fossil and subfossil canids that are said to be the most recent common ancestor of wolves and coyotes simply aren’t.  Instead, all of these species that are classified in Canis are likely a mix of evolutionary dead ends, like the dire and Armbruster’s wolf, or could be hidden ancestors of extant canids that aren’t wolves or coyotes.

For example, black-backed and side-striped jackals diverged from the rest of Canis and its allies at about the same time that Eucyon was diverging from Canis. It is possible that there are many relatives of these particular dogs that are hidden in this vast sea of Canis fossils.

The new discovery about the coyote’s split from the wolf also means that any remains of North American canid that are listed as coyote that date to 1 million years before present are not coyotes. What they actually were is a very good question.

We’ve spent a lot of time assuming that coyotes and wolves were quite divergent. We know now that they really aren’t, but when we look into the past at all the “wolves” and “coyotes” that came before, we see how this genus became so successful. It can easily evolve into big game-hunting forms, but the real success is in its ability to assume the size and shape of the generalist predator. Phenotypic plasticity is a wonderful thing for a lineage to possess.

But the real message of the new discovery about wolves and coyotes should be is a cautionary tale about paleontology. Paleontology is a wonderful science, and it makes amazing discoveries every day, but when its faced with a lineage of animals where phenotypic plasticity and tendencies toward parallel and convergent evolution are commonplace, it is bound to make errors. Paleontologists aren’t examining flesh and blood that can have its molecules tested for relationships. They are measuring anatomical characters and determining phylogenetic relationships based upon the similarities of these characters.

Which works well.

Until you get something like wolves and coyotes, where there are many ancient fossil and subfossil remains that look like they could be ancestors of either.

But the DNA says they aren’t.

And paleontology would have problem catching the inverse. There are many species that we’ve discovered only through DNA testing. African butterfly fish in the Congo and Niger basins look identical to each other, but they have been isolated from each other for 57 million years. I have yet to see this species split into two, but if they were mammals, you could bet they would be placed in distinct species in heartbeat.

Paleontology is missing some really important things we’ve since found out through molecular analyses.

And paleontologists know this.

They are working with the data they have, and by definition, it’s going to be more incomplete than genetic studies.

Science is provisional. Different disciplines and methodologies are going to come up with different answers. It’s pretty amazing that one genome-wide assay study can wipe out so much literature in paleontology.

These debates have been raging for years.

And it turns out that everyone was actually wrong.

Update 21 August 2016:  It turns out that I missed a paper that actually did some limited DNA analysis and found that Canis nehringi was pretty much a South American dire wolf, as in it was likely the same species as the North American dire wolf. Canis gezi, however, was  more closely related to the modern maned wolf and had been incorrectly identified as a wolf. So let this stand as a correction to the error above.

 

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Ethiopian wolf hunting strategies

From the BBC’s The Hunt:

 

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Canis cedazoensis

Canis cedazoensis was an early species of the wolf-coyote-jackal tribe. It lived what is now the American Southwest and Northern Mexico until 300,000 years ago. It probably scavenged kills of bigger predators and lifted off the fawns of the various species of pronghorn.

Conventionally, we believed that the lineage from which this jackal-like canid gave rise to the wolf, the coyote, and the golden jackal. We based these assessments on comparative morphology from fossil and subfossil remains, and it all made sense.

These jackal-like forms entered Eurasia and Africa. They gave rise to the Xenocyon, the first wolf-like canid to evolve of this lineage.  The Xenocyon gave rise to the dhole and the African wild dog. Then the actual wolves evolved in Eurasia, and they walked back into North America to found the Armbruster’s wolf and the Dire wolf. They spread to South America, and endemic North American wolves, Canis edwardii and the putative red wolf evolved out of an unrelated jackal-like line.

The coyote descended from some sort of jackal-like canid in North America and a least a million years of evolution separates the coyote from the modern gray wolf.

The most recent study that examined full genomes of various wolves, dogs, and coyotes revealed that the separation between coyotes and gray wolves happened only 50,000 years ago. This finding pretty much destroys all this thinking.

We’ve conventionally thought of the lineage starting out with jackal-like forms that evolve into wolf-like forms, but the truth is we have a lineage that started out with jackal-like forms. Wolf-like forms evolved at least twice from this lineage, and jackal-like forms have evolved from wolf-like forms as well.

What we’ve missed that just as the Xenocyon and the dhole and African wild dog have evolved into wolf-like forms in parallel to actual wolves, the real story of Canis is that there has been a constant tension between selection for wolf-like traits and jackal-like traits. The coyote is a wolf that has re-adapted itself to the jackal-like form. To become a jackal is to become a generalist again. To evolve towards the wolf is become an apex predator and be forced to hunt for large game to survive.

What we know from the fossil record is the story of wolves and dogs and coyotes and their kin is that it began with “jackals.”  Paleontology says that North America is where this story got started, but the oldest species in this lineage of dogs lives in Africa.

I would love to know the full story.

Canis cedazoensis is a creature lost to time. If we could see one, maybe we know some answers. Maybe we would see something very much like a black-backed jackal. Maybe it would answer some questions.

And it would probably raise more.

Yet more of the mystery to which we should humble ourselves.

It began with jackals, and in the Anthropocene, it may end with them as well. The coyote and Eurasian jackal have continued to spread their range. The coyote is from from Alaska and Newfoundland to Panama– on its way to Colombia. The Eurasian jackal (the “golden jackal,” as it is normally called) spreads north and west through Europe. Both are generalists of the jackal type.

Phenotypic plasticity and convergent evolution have played quite a game with this part of the dog family.

Science is always provisional, and often takes just one profound discovery to turn over the apple cart.

And oh, has it been turned!

 

 

 

 

 

 

 

 

 

 

 

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