Canis lupus hominis

Photo by Nicola Williscroft at Twycross Zoo, UK.

Only two species of wild dog are found in both North America and South America.

The Urocyon gray fox that yaps in the night from the dense brush near my home ranges all the way down to Colombia and Venezuela. It’s an unusual animal, derived from an evolutionary lineage that split off from the rest of the dog family 9 or 10 million years ago.

The other species that is found on both continents is the bush dog (Speothos venaticus). When I say that it ranges on both continents, I mean that it does range into extreme southernmost Panama. Panama used to be part of Colombia, and there actually is some debate as to which continent it actually belongs.

The bush dog is the smallest wild dog to hunt in packs, a trait that it has evolved in parallel with the wolves, the dholes, and African wild dogs. At one time, it was believed to have been a type of dwarf New World dhole. Like the dhole and African wild dog,  the bush dog has the “trenchant heel” dentition that allows the dog a sharper cutting surface when it eats meat.

Besides the unusually smug expression on this bush dog, one can see another feature prominently displayed in the photo– truly webbed feet.  Retriever and Newfoundland dog people like to brag about how webbed their dogs’ feet are, but they are nothing like a bush dog’s. Bush dogs and the little studied short-eared dog have this feature, which assists them in maneuvering around in flooded forests and through large rivers.

The closest living relative to the bush dog is the maned wolf, as known as the “real red wolf,” but the two species do not resemble each other in the least. The maned wolf is a long-legged, rather ostentatious creature that looks something like what would happen if one tried to make a wolf out of a red fox. It is a creature of the savannas and open marshland, while the bush dog is more of a habitat generalist.

The bush dog is like a naturally-occurring basset. Some native people of South America have tried to tame them, but no one has been able to establish a domestic population.

South America is currently home to the most diverse genera of wild dogs currently in existence. It also has some of the most bizarre.

The dog family first evolved in North America around 40 million years ago, but over time, the Northern Hemisphere and Sub-Saharan Africa became dominated by two basic types:  Canis and the genera that should be in Canis (dhole and African wild dog) and the true foxes (the genus Vulpes). Currently, if we adhere to cladistic classification, there are only three species outside of Canis/should be-Canis  and Vulpes:  the bat-eared fox (Otocyon megalotis), the raccoon dog (Nyctereutes procyonoides), and the aforementioned Urocyon gray foxes.

In South America, there are five different genera. They are all more closely related to the Canis/should be Canis species, but they are all quite distinct. These lineages evolved in North America alongside the ancestors of the Canis/should be Canis species, but for whatever reason became found exclusively in South America, where they wandered down over the past 3 million years.

Outside of South America, no one knows much about these animals, and because most of these animals are quite elusive, very few people in those countries know much about them either.

South America’s canids are a good place to play around with speculative evolution. This is what happens when the diverse endemic North American canids wind up invading the tropics and then wander down to the Southern Hemisphere.

If you look at all the wild dogs of the Old World and North America, the body type is really conservative.

You don’t see anything like a bush dog, a short-eared dog, or a maned wolf.

(Unless you’re looking at domestic dogs, which are the most bizarre animals in the whole order Carnivora!)