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Posts Tagged ‘dhole’

Dholes kill a gaur calf

Gaur or “Indian bison” are the largest species of bovine. Dholes are about the size of Eastern coyotes, but they are superb hunters in a large pack.

These are Kipling’s “red dogs” at work.

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The narration is very hard to hear, but it is amazing footage:

Source.

These dholes truly are Cuon alpinus, the mountain dogs.

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This phylogenetic tree comes from a study that used a high quality draft genome sequence of the domestic dog to make important comparisons within domestic dog breeds and also to make some comparisons with their relatives.

One of the most interesting discoveries in the this study was that the genus Canis as it is currently classified is paraphyletic.

Paraphyly is a major problem in cladistic taxonomy, for the goal is to have genera, orders, and families all to reflect common ancestry.

But if one looks at the species currently classified as belonging to the genus Canis on this phylogenetic tree, there is a gap between the two endemic African jackals– the side-striped (Canis adustus) and black-backed (Canis mesomelas)– and the other species in the genus Canis– the Ethiopian wolf (Canis simensis), the golden jackal (Canis aureus), the coyote (Canis latrans), and the Holarctic wolf/domestic dog/dingo/New Guinea singing dog species (Canis lupus). This clade of Canis  includes the interfertile Canis, where hybridization is possible between all members.

The two endemic African jackals cannot cross with any other members of the genus. Let me repeat that:  there are no black-backed jackal or side-striped jackal hybrids with domestic dogs or any other dog species. Some people claim that pariah and village dogs from Africa have ancestry from these jackals, but no genetic evidence has been provided to confirm the existence of these hybrids.

If one follows that phylogenetic tree, the gap between the two groups of Canis is filled with two species. These are the so-called “hunting dogs,”  which we call the dhole (Cuon alpinus) and the African wild dog (Lycaon pictus). The most common hypothesis about the origin of these dogs is they are both derivatives of an extinct wolf-like dog that was called Xenocyon lycaonoides. There is some debate about whether both of these dog descend from them, but the bulk of the literature suggests that they derive from this species.  Xenocyon filled the same ecological niche as wolves eventually did, but it was not part of the wolf lineage.

The conventional thinking on Xenocyon is that it evolved into the dhole and African wild dog species, but there is at least one study that suggests that the African wild dog derived from a different lineage. I am a bit skeptical of this study because it was based upon tooth morphology. Tooth morphology is one aspect that has led us to believe that African wild dogs and dholes are related, but one should keep in mind that tooth morphology once led us to believe that dholes and African wild dogs were closely related to the South American bush dog (Speothos venaticus), which we now know is part of the South American canid clade.  If these tooth adaptations can evolve from that such disparate lineages, I don’t see why they couldn’t have evolved from unrelated lineages in the past.

Whatever the exact ancestors of the dhole and the African wild dog, they create a gap in the phylogenetic tree between the interfertile Canis and the endemic African jackals.

That means that we have to make Canis monophyletic.

The easiest way to do this is to get rid of the genera Cuon and Lycaon.   The African wild dog becomes Canis pictus (the painted dog) and the dhole become Canis alpinus (the mountain dog).  I don’t recommend going with Canis lycaon to denote the African wild dog. This name has been bandied about for the proposed but now largely falsified Eastern wolf species, and using this name for the African wild dog would just make things very confusing.

If Cuon and Lycaon are no longer unique genera and the species within them are reclassifed as Canis, the entire genus becomes monophyletic.

I would recommend this recourse.

However, one could keep Cuon and Lycaon if one created a unique genus for the black-backed and side-striped jackals. Several genus names have been proposed for jackals, but I don’t know if we have a good system for coming up with one. The study that suggests that Xenocyon and the African wild dog suggests that we use the Lupulella for these two jackals, which would connect with what have been called primitive jackals that were living in Northwestern Africa during the Pleistocene. These primitive jackals had morphology that was very similar to the modern raccoon dog (Nyctereutes procyonoides). Black-backed jackals in their current form trace to the early Pleistocene in East Africa, so they likely didn’t derive from these primitive ones in Northwest Africa. And it is unlikely that side-striped jackals evolved from them either, for it is a newer species than the black-backed jackal and is usually considered a sister species with the black-backed jackal. Indeed, it is also possible that side-striped jackals derived from black-backed jackals that were adapted to living in dense forests.

The skull morphology of the ancient Lupulella suggests that it may not have been a jackal at all, but it may have been a dog derived from the raccoon dog lineage that just happened to have some features in common with modern jackals.

Raccoon dogs and bat-eared foxes are currently considered basal foxes.  At one time, they were both considered basal to the entire dog family, but now the only odd-ball basal canid species are the gray foxes in the genus Urocyon. It is at least as likely that the extinct Lupulella species were jackal-like derivatives of the raccoon dog lineage, and combining modern black-backed and side-striped jackals with these species is not well-advised.

Therefore, the best course of action is to move the African wild dog and the  dhole into Canis.

However, I do think we need to create subgenera within Canis to denote phylogenetic relationships. These subgenera should create three clades: one for the interfertile Canis, one for the hunting dogs, and one for the two endemic African jackals.

This is perhaps the best way to do away with a clumsy paraphyletic genus.

And one should understand that the genus Canis is not the only paraphyletic clade in zoology. The truth is we have lots to figure out about the exact evolutionary relationships that exist between different species.  There are some species, like the South American red brocket deer (Mazama sp.), that likely contain several different species from very distinct evolutionary lineages that have been combined within the same species based upon nothing more than superficial reasons.

With Canis, fixing this problem is pretty easy. However, it might be difficult to get the scientific names changed to reflect phylogeny properly.

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Love in the bush

 

These two bush dogs trying to increase the numbers of their species, which is considered near threatened in the wild.

These little dogs form packs of up to 10-12 individuals, and although they weigh only 10 to 18 pounds, they’ve been known to bring down tapirs and peccaries.

Bush dogs, dholes, and African wild dogs have an extra long “blade” on their lower carnassials that allows these wild dogs to more efficiently slice through flesh. These blade is called the “trenchant heel.”

Dholes and bush dogs were once thought to be close relatives. Not only do they share the trenchant heel, they also are unique among canids in that they have only 40 teeth. All other dogs have 42.   However, dholes are also relatively small, weighing only 22 to 55 pounds, and bush dogs are the smallest of all pack hunting canids.  But both the dholes and bush dogs have reputations for killing prey much larger than themselves. There is a common legend that dholes kill tigers, even though it’s much more likely that the tiger would stalk dholes.  Amur tigers keep the northernmost dholes at relatively low densities, but Amur tigers are known for their penchant for eating both wolves and dogs. A dhole would just be a wolf of another flavor.

But when you combine the dentition with the legendary behavior of both species bringing down large prey, it is easy to see why people put the two together.

But now we know that the bush dog, despite its short legs, is actually most closely related the rangy maned wolf of South America– which is not a true wolf at all but a member of the South American canids clade.  The dhole is very closely related to the genus Canis, and it probably should be classified within it. Its exact relationship to the African wild dog is still debated, as is the exact natural history of the dhole.

But it’s obvious from the genetic studies, that dholes are not related to bush dogs at all. (See this phylogenetic tree, which was drawn from sequencing the dog genome to see where the various dog species.)

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This post is working up to something else, so be ready for it.

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Dhole with puppy

At the San Diego Zoo.

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This plate comes from The Animal Kingdom (1897) by Hugh Craig.

Today, we’d laugh at such classification.  We know know dholes are far too distantly related to dogs to have even been considered a possible ancestor.

If one thinks about it, dholes, dingoes, and certain South Asian pariah dogs are similar in appearance. They roughly the size of a mid-sized Western domestic dog, and the dholes, dingoes, and many pariahs from that part of the world are golden red in color.

In light of a similar appearance, one can see how easy it would be classify them all together.

There were even some early theorists on the origins of the domestic dog who thought the dhole had to have been the sole wild ancestor. While living  in Nepal in 1833, the British ethnographer Brian Houghton Hodgson was able to raise a dhole from a tiny pup, where it grew up as friendly and docile as any dog. Based upon his observations of this tame dhole, he deemed the species Canis primaevus– the primeval dog. He also contended that with the exception of the dhole’s lower post-carnassial molars, the dhole skull was quite similar to a dingo or pariah dog, and because the dhole is more socially tolerant than the wolf, even sharing its kills with jackals and pariah dogs, it might be more easy for ancient humans to habituate them to their presence.

I think it is interesting that man has never domesticated the dhole. It seems to have traits that would have made it a better choice for domestication than other wild dog species than have been domesticated. An attempt to domesticate the red fox occurred in Jordan 14,000 years ago, and the Yaghan people of Tierra del Fuego had fully domesticated “otter hounds” that were derived from the culpeo. (Domestic dogs are older than the Natufian, so just ignore that hype about the red fox being domesticated before the dog. It just isn’t so.)

The dhole has never been among the ranks of the domesticated.

And these attempted domestication-attempts were ultimate failures. Only the domesticated wolf ever proved to be successful.

We now have conclusive evidence that all dogs that exist today are derived from wolves. In fact, it many not even be accurate to refer to dogs as their own species– I certainly don’t.  Dogs are nothing more than a form of wolf that has evolved to live with man, and both natural and artificial selection have acted upon it to reach this end.

My only question is why the wolf was successfully domesticated and not other social wild dogs.

Why the wolf and not the dhole?

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Dholes hunting chital (axis deer)

Source.

Dholes do hunt in packs, but it is thought that they form large packs for a different reason.

Because they evolved to live in the same areas as tigers, leopards, and Asiatic lions, they needed to form larger packs to protect themselves from predation.

Something very similar can be seen in the African wild dog or “painted wolf” species, which lives where there are lions, leopards, and spotted hyenas that really love to kill them.

Wolves evolved where they are essentially the top predator. Only tigers and man have been proven to significantly limit wolf numbers, but wolves themselves limit the numbers of black bears (both Asiatic and American), coyotes, golden jackals,  many species of foxes, and cougars, just to name a few.

Wolves don’t need big packs to protect themselves.

Dholes and African wild dogs do.

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