Posts Tagged ‘South American bush dog’

Extant South American Canids are Ancient Relics

August 16, 2017

Several species of medium-sized canids native to South America descend from species that formerly occupied North America.  The extant bush dog (Speothos vunaticus), maned wolf (Chrisocyon brachyuras), and the recently extinct Falkland Islands wolf (Dusicyon australis) are (or were) similar to primitive dogs that occurred across North America during the late Miocene and Pliocene.  The emergence of the Canis genus (wolves and coyotes) early during the Pleistocene competitively excluded these primitive dogs from North America, but their ancestors pushed through the jungles of Central America, and they colonized South America where they still thrive today when not persecuted by man. The tropical rain forests of Central America served as a geographical barrier that prevented Canis species from following their primitive relatives.  Though Canis species may be more adaptable overall, their primitive relatives were better able to withstand tropical conditions, a factor that saved them from extinction.

The South American bush dog is a widespread but uncommon pack-hunter that preys on large rodents, peccaries, and rheas.  One genetic study suggests they are most closely related to maned wolves, but another more recent genetic study determined they are most closely related to African hunting dogs.  A species similar to the African hunting dog lived in North America as late as the mid-Pleistocene, so the bush dog may very well be an offshoot of this canid line.  The maned wolf is a solitary species, not a pack-hunter–additional evidence supporting a closer evolutionary link between bush dogs and pack-hunting African dogs, rather than the maned wolf.  The bush dog was known from fossil evidence found in a Brazilian cave before it was recognized as an extant species.

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South American bush dogs.  They are descended from primitive dogs that roamed North America before the Canis genus dominated that continent.

The Falkland Islands wolf was the only mammal species native to the Falkland Islands.  It was a completely naïve species, unafraid of man, and was hunted to extinction by the late 19th century.  Settlers coveted its furry coat and were afraid it would kill their sheep.  Actually, the diet of this species is unknown, but it probably subsisted on penguins, geese, and sea shore scavenging.  How this species colonized the Falkland Islands, located 285 miles from the mainland of South America, was a mystery until recently.  Geologists discovered underwater ridges connected to the mainland that were above sea level during Ice Ages.  A narrow 20 mile straight between the ridges and the Falkland Islands froze into solid ice during winters of the Last Glacial Maximum (~16,000 years ago), allowing the canids to cross.  They may have been hunting penguins on the ice, leading them to the islands.  No other mammal found motivation to cross the ice bridge.

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Extinct Falkland Islands Wolf.  Unfortunately, they had no fear of people.

Genetic evidence suggests the Falkland Island and maned wolves are most closely related to false foxes (Lycalopex sp.), 6 species of which are found in South America today.  However, the Tibetan fox is the maned wolf’s closest living relative.  The Tibetan fox is likely related to the ancestors of all false foxes.  An extinct species of maned wolf (C. nearctus) lived in North America during the Pliocene.  Fossil evidence of this species has been found at sites in Arizona, California, and northern Mexico.  The maned wolf has long legs that help it look over tall grass for rodents–its main prey item.  Genetic evidence shows maned wolf populations increased during Ice Ages when grasslands expanded and contracted during interglacials.  Pliocene environments were often dry and included an expansion of prairie habitat, so it’s likely the North American maned wolf also had long legs.  The fossil evidence of C. nearctus is limited to lower jaws and teeth, so it’s not known how long its legs were.  Maned wolves are omnivorous, and they are important dispersers of seeds.  They often defecate on leafcutter ant nests, and the ants move the viable seeds, helping them germinate.

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Maned wolf.  Maned wolves lived in North America during the Pliocene.

The maned wolf grows to about 50 pounds, but a larger genus of primitive dogs lived in North America until the early Pleistocene.  Theriodictis hunted megafauna in Florida.  Species from the Canis genus outcompeted them in North America, but they continued to thrive in South America until the late Pleistocene extinctions of the megafauna.

Reference:

Nyakatura, K.; et. al.

“Updating the Evolutionary History of Carnivora (Mammalia): A New Species Level Super Tree Complete with Divergence Time Estimates”

BMC Biology 10 (12) 2017

Tedford, Richard; X. Wang, B. Taylor

“Phylogenetic Systematics of the North America Fossil Caninae”

Bulletin of the American Museum of Natural History 2009

 

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