African Hunting Dogs Lived in North America during the Middle Pleistocene

The African hunting dog (Lycaon pictus meaning painted wolf) stars in many nature documentaries, but few people are aware that close relatives of this species formerly lived across Eurasia and even into North America.  At least 2 different species occurred in North America during the middle Pleistocene between ~1.5 million BP-~300,000 BP.  Fossil remains of Xenacyon lycaonoides were excavated from 2 sites in Alaska and 1 in the Yukon.  The first paleontologist who looked at these specimens misidentified them as dhole (Cuon alpinus) teeth, but a more recent examination of the dentition determined they belonged to a canid more closely related to African hunting dogs.  These scientists also examined the only other dhole fossils found in North America (from San Josecitos Cave in Mexico) and did confirm that identification.  The other American species of canid closely related to the African hunting dog was Xenacyon texanus, and it’s known from just 1 fossil locality–Rock Creek in northwest Texas.  The sum total fossil remains of X. texanus are part of 1 jaw with teeth, a leg, and a shoulder fragment.  Based on this scant anatomical material, scientists believe X. texanus was slightly larger the X. lycaonoides which was about the size of a timber wolf.

Two extinct and little known species of canid, closely related to present day African hunting dogs, lived in North America during the middle Pleistocene.

Dholes tearing up a deer.  Fossil remains of this canid have been found from just 1 site in North America.  It originated in Asia, yet it inhabited Mexico during the late Pleistocene.  It must have been more widespread in North America than the fossil record indicates.

Wolf fossils in North America are much more common than those of X. lycaonoides, X. texanus, and Cuon alpinus.  This suggests these species of hunting dogs didn’t compete well with American wolves.  During the middle Pleistocene X. texanus would have occupied the same ecological niche as Armbruster’s wolf (Canis armbrusteri), the probable evolutionary ancestor of the dire wolf (Canis dirus).  Nevertheless, X. texanus did live in North America long enough to have evolved into a different species from X. lycanoides.  Obviously, they were more widespread and successful than the fossil record indicates.  It’s possible this species persisted into the late Pleistocene but was restricted to regions where their remains were not likely to be preserved.  The only dhole fossils found in North America were discovered in Mexico, yet this species originated in Asia, crossed the Bering landbridge, and must have occupied large areas of North America before colonizing Mexico.  Dholes co-existed with dire wolves and timber wolves (Canis lupus) in North America for some undetermined length of time.  The oldest dire wolf fossil dates to 252,000 BP (from a uranium-series dated deposit in South Dakota).  Timber wolves crossed the Bering landbridge 100,000 years ago and co-existed with dire wolves in western North America until the end of the Pleistocene.  It’s not known when dholes crossed the Bering landbridge.  Timber wolves and dholes are not known from the fossil record of southeastern North America.  I think dire wolves kept these other big game-hunting canids from occupying this more wooded region where prey was less abundant than on the grassy plains of the west.

The Rock Creek Fossil Site

Rock Creek, the only known fossil site where Xenocyon texanus has been found, is located just north of Plainview, Texas, represented by the dot on this map.

The Rock Creek fossil site is located just north of Plainview, Texas.  This is the only locality where remains of X. texanus have ever been found.  E.L. Troxell excavated this rock quarry and published his findings in 1915.  Along with the rare canid, he found the remains of gopher tortoise, giant tortoise, Harlan’s ground sloth, glyptodont, Imperial mammoth, flat-headed peccary, camel, llama, Soergel’s musk-ox, and horse.  He identified the remains of another canid as dire wolf, but he was probably in error.  The geological formation where these fossils were found is thought to be no younger than 400,000 years BP.  Dire wolves probably didn’t evolve yet, so the canid remains probably should be referred to as Armbruster’s wolf.

The composition of species excavated from Rock Creek suggests the region during this climatic phase consisted of arid grassland and scrub with milder winters than those of today.  Some scientists assume it was frost free due to the presence of giant tortoise, but I believe this species could survive light frosts.  Although winters were warmer then, it’s not safe to assume there were no frosts.  The horses, camels, and peccaries likely served as dinner for X. texanus.

References:

Tedford, Richard; et. al.

“Philogenetic Systematics of North American Fossil Caninae (Caninae: canid)”

Bulletin of the American Museum of Natural History 2009

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Did the dhole (Cuon alpinus) range into southeastern North America during the Pleistocene?

Photo of dholes from google images.

John Valliant sets the scene in his excellent non-fiction book, The Tiger, with a description of Russia’s far eastern flora and fauna.  Of the latter he mentions the dhole (Cuon alpinus), a medium-sized canid that no longer exists where Siberian tigers now roam, but still clings on to its last strongholds in India and a few neighboring countries.  Upon reading this, I remembered Bjorn Kurten’s brief account of dhole fossils found in North America.  In Pleistocene Mammals of North America he stated that dhole fossils were found in at least 3 sites in Alaska and 1 in Mexico. This means the species existed throughout the center of North America and perhaps in other regions as well.

Richard Reynolds, formerly curator of the Los Angeles Museum of Natural History, first identifed 7 specimens (lower jaws and teeth) of dholes that were excavated from San Josecito Cave in northeastern Mexico.  In 1971 Ronald Nowak examined the specimens and confirmed that they were from dholes.  Dr. Nowak is the world’s foremost authority on Pleistocene canids.  However, the specimens weren’t described in the scientific literature until 2009, and scant attention was paid to the role dholes played in North American ecology.  I can remedy that, at least on my blog.

Map of location of San Josecitos cave, and a photo of early excavation at the site.  From “The Cave of San Josecito Mexico: New Discoveries of the Vertebrate Life of the Ice Age” by Chester Stock in Engineering and Science Monthly (circa 1940?).

Map of ecological corridors from Mexico to the rest of North and Central America.  During the Ice Age when dholes were present, mixed pine forests displaced what’s now xeric scrub.  Dholes could have colonized the southeast from the gulf lowland corridor.  From “Effects of Pleistocene Environmental Changes in the Distribution of Community Structure of the Mammalian Faunas of Mexico” by Gerardo Ceballos; et. al. in Quaternary Research 73 (2010) page 470.

I think it’s quite possible dholes periodically colonized parts of southeastern North America but without fossil evidence, there is no way of knowing for sure.  Their preferred habitat is montane forests of about 3000 feet in elevation, though they can adapt to steppe-like environments, and jungles.  The mixed forests in the piedmont and mountain regions of what’s now Mississippi, Alabama, Georgia, Tennessee, and the Ozarks of Arkansas would have been ideal and potential habitat for them.  They must have found a suitable corridor of habitat along the Rocky Mountains because they found their way from Alaska to Mexico.  Despite the lack of fossil evidence, they must have inhabited the  region in between.  How far east they ranged is unknown. Florida’s rich fossil record draws a blank for dholes.  However, Florida’s fossil record also draws a blank for red wolves (Canis rufus).  It’s likely red wolves were regionally present in low numbers during the Pleistocene because they became the dominant canid here following the extinction of dire wolves.  Moreover, collared peccary and giant short-faced bear (Arctodus simus) fossils weren’t known from Florida until within the last 5 years, so dhole fossils may yet be discovered somewhere in the southeast.  As the old chiche` goes, absence of evidence is not evidence of absence.  There may be evidence  from Georgia–a tibia from a medium-sized canid was excavated from Kingston Saltpeter Cave in Bartow County.  Unfortunately, scientists require skulls and teeth to determine canid species.  The tibia could be from a dhole…or a coyote, a juvenile wolf, or even a paleo-indian’s dog.

One further note on the absence of dhole fossils in the southeast–the odds of an individual animal becoming a fossil are unknown but may be 1 in a million.  900,000 dholes could have lived in the region over the millenia, but that number wasn’t high enough to significantly increase the chances of one of them becoming a fossil.

How did dholes interact with North America’s Pleistocene fauna?  Dholes live in packs of 10-12 but sometimes multiple packs temporarily merge forming groups of up to 40.  Despite including individuals only weighing 25-40 pounds, these expanded packs have been reported to successfully attack large buffaloes and even tigers.  The packs do suffer considerable mortality when battling these ferocious foes.  A tiger can kill a dhole with just a blow from its paw.  Perhaps, dholes occasionally attacked saber-tooths.  Maybe that’s why they’re not common in the fossil record–saber-tooths may have dispatched a whole foolhardy pack.  Dholes are less intelligent than wolves. 

Dholes may on occasion attack large dangerous prey, but one study found that their preferred prey selection was of individuals weighing between 60-350 pounds, and the average kill weighed 86 pounds.  Deer, peccary, juvenile horses, and bison calves would’ve been their preferred prey in North America.  By comparison, in that same study, the average kill of a tiger was 180 pounds.  So dholes probably selected for smaller prey than dire wolves, saber-tooths, scimitar -tooths, jaguars, and giant panthers (Panthera atrox), and thus occupied a slightly different ecological niche.

In a correspondence with Dr. Nowak I suggested that, based on their rarity in the fossil record, dholes didn’t compete well with dire wolves.  He thinks it was competiton with timber wolves (Canis lupus) that may have kept their numbers low here and possibly caused their extirpation on the continent.  However, I hypothesize that it was the extinction of the megafauna, not interspecific competition, that led to their demise in North America and Europe.  The existence of large amounts of meat in the form of mammoths, mastodons, and giant ground sloths was a boon to carnivores and scavengers.  Though dholes didn’t actively hunt them, when one of these great beasts died a natural death, they provided a feast for predators of all kinds, contributing to an increase in their survival rate and diversity.

I can just imagine a pack of quick dholes aggravating a saber-tooth or giant bear until they abandoned the carcass.  But today, dholes only survive in ever shrinking territory.  It would be a shame to lose them.

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San Josecito Cave

San Josecito Cave is a spectacular fossil site, eighty feet in depth.  The matrix originally excavated was 60 feet thick in fossils.  Scientists  are still excavating the site, even though excavation began in the 1930’s.  At least 62 species of bird fossils have been found here.  Here’s a partial list of species found at the site.  * denotes extinct species.

*Shasta ground sloth

*Jefferson’s ground sloth

dhole

coyote

gray wolf

*dire wolf

cougar

*saber-tooth

*giant panther–Panthera atrox

jaguar

black bear

*Florida spectacled bear

hog-nosed skunk

vampire bat

southern bog lemming

pocket gopher

yellow bellied marmot

cottontail rabbit

Sylviligus leonensis–an extinct species of rabbit

*mountain deer–Navahoceras fricki

white-tail deer

*llama

horse

*an extinct species of pronghorn–Stockoceras conklingi

*an extinct subspecies of mountain goat–Oreamnos harringtoni

*walking eagle

golden eagle

*Grinnell’s Crested eagle

white-tailed kite

Harris Hawk

Gray Hawk

Ferriganous hawk

red-tailed hawk

northern harrier

prairie falcon

*terratorn

black vulture

California Condor

*a large extinct vulture–Neogyps errans

*a small extinct vulture–Neophrontops americanus

*a large extinct subspecies of roadrunner

turkey

Montezuma quail

wood quail

band-tailed pigeon

mourning dove

pied-billed grebe

wood duck

ruddy duck

dabbling duck

harlequin duck

king rail

Virginia rail

coot

*an extinct stork–Ciconia

pinyon jay

scrub jay

raven

woodcock

thick-billed parrot

maroon-fronted parrot

pygmy owl

elf owl

saw-whet owl

great horned owl

spotted owl

barn owl

eastern screech owl

whiskered screech owl

long-eared owl

short-eared owl

plover

common poorwill

robin

black crowned night heron

curlew

meadowlark

red-shafted flicker