A Good Narrative about the American Cheetah (Miracinonyx trumani) may be Ruined but maybe not

The close physical similarity between the extinct cheetah (Miracinonyx trumani) of Pleistocene North America, and the still extant cheetah (Acinonyx jubatus) of Africa and Asia caused confusion among paleontologists.  The anatomy of both species shared characteristics of a cat built for great speed.  Paleontologists thought cheetahs originally evolved in North America and later colonized Asia and Africa.  Then, based on a re-evaluation of the fossil evidence and new genetic studies, scientists realized the similarity between the Old World cheetah and the North American cheetah was just a case of convergent evolution that occurs when 2 unrelated species evolve similar traits to help them adapt to similar environments.  The 2 species were not as closely related as formerly thought.  Instead, the North American cheetah evolved from an extinct Asian cougar (Puma pardoides) that crossed the Bering Land Bridge over 6 million years ago.  After Puma pardoides colonized North America, the species diverged into 3 lineages.  One line led to an animal adapted for hunting on the grassy plains–M. trumani.  Another line evolved into the jaguarundi (Puma jagouaroundi), a small cat of tropical brush habitat.  The third line evolved into the modern cougar (Puma concolor), a generalist species well adapted for living in a wide range of environments.  Puma concolor doesn’t occur in the fossil record until ~500,000 years BP, but I believe its evolutionary predecessor was Miracinonyx inexpectus.  Temporally, fossil material of Puma concolor and M. inexpectus doesn’t overlap. The latter was likely the late Pliocene/early Pleistocene version of the cougar.  Miracinonyx studeri, a scientific name used in some studies, is merely a synonym for M. inexpectus.

Artist’s depiction of an American cheetah chasing a pronghorn.  Pronghorns can run up to 60 miles per hour.  No extant predator in North America even comes close to this.  An analysis of the anatomy of the extinct American cheetah suggests it was built for this kind of speed with long legs, flexible spine, and large nasal passages for rapid air intake.

Pronghorn antelopes (Antilocapra americana) reach speeds far exceeding any extant predator living in North America.  Scientists hypothesized they evolved this capability to outrun a predator that is now extinct.  They believe M. trumani was that predator.

A few years ago, paleontologists excavated fossil material they identified as M. trumani from several caves within the Grand Canyon.  This high elevation habitat was home to mountain goats (Oreamnos harrington and Oreamnos americanus) not pronghorns.  These scientists proposed the American cheetah, at least at this locality, occupied a niche like that of an alpine snow leopard (Uncia uncia), a big cat that hunts on steep rocky slopes.  It would seem the narrative about the American cheetah and pronghorn might be ruined.  However, Ross Barnett, author of a study referenced below, is not convinced the fossil material found in the Grand Canyon is from American cheetah.  These specimens were identified by comparing them with bones from modern cougars and other American cheetah remains.  M. trumani was somewhat larger than modern cougars, so it was assumed the Grand Canyon material represented American cheetah, not cougar.  Dr. Barnett suggests the material should have been compared with fossil remains of Pleistocene cougars which were on average larger than modern cougar.  The Grand Canyon material may actually be Pleistocene cougar.  Cougars are well adapted for living on steep slopes. So the narrative of the American cheetah and the pronghorn may not be ruined. Incidentally, the cougars that lived in North America were an extinct ectomorph–all modern North American cougars descend from a small population originating from eastern South America.

There’s no fossil evidence M. trumani ever lived east of the Mississippi River.  But M. inexpectus and Puma concolor are a common enough (for a large carnivore) find in fossil sites throughout southeastern North America.

Some now refer to the American cheetah as the “false cheetah.”  I don’t think the adjective “false” should be used to describe an animal, simply because humans were once confused about its evolutionary relationships.

References:

Barnett, Ross; et. al.

“Evolution of the Extinct Sabre-tooths and the American Cheetah-like Cat”

Current Biology 2005

Hodnett, Jean-Paul; et. al.

“Miracinonyx trumani (Carnivore: Felidae) from the Rancholabrean of Grand Canyon, Arizona and its Implications for the Ecology of the American Cheetah”

Programs and Abstracts, Journal of Vertebrate Paleontology 2010

The Mystery Cat of Pleistocene Georgia

Most small species of cats are adept tree climbers, but the margay (Leopardus wiedii) excells. It hunts, copulates, and raises its young in trees, making it as arboreal as a monkey or squirrel.

The margay is about the size of a large house cat.  It is an arboreal species.

The margay is able to climb head first down trees, and its wrists are built much like those of a squirrel’s.  Click on the below link to the youtube video of a margay.  Note how it can hang upside down using just its rear paws.  Note also its athletic ability to leap from tree limb to tree limb.

http://www.youtube.com/watch?v=ef129AsFfMA

The margay is a nocturnal hunter, preying upon birds, birds’ eggs, frogs, lizards, rodents, monkeys, and probably bats.  They also eat fruit.  Like tigers, they use audible mimicry to lure prey.  They’ve been observed imitating the cries of a baby monkey to attract parent monkeys to their doom. (Tigers imitate the mating bugle of elk.)  Not all prey is defenseless, however.  Brazilian squirrels gang together and drive margays away.

Today, the margay ranges throughout Central and South America, but fossil evidence of a margay-like cat has been found from 12 sites in Florida and 2 in Georgia.  Jaw bones of this mystery cat come from Ladds in Bartow County, Georgia and the Isle of Hope site in Chatham County near Savannah–evidence this species occurred throughout the state during the Pleistocene.  The fossils from all the sites where this species has been found likely date from a warm interglacial period.  Some scientists think these fossils represent an extinct species (Leopardus amnicola), while others consider it an extinct, large subspecies of margay (Leopardus wiedii amnicola).  The modern margay requires dense forest habitat, and it’s likely this species or subspecies did too, probably explaining why its fossils are found in deposits dating to interglacial periods.  During interglacials forested habitats expanded.

Sketch of the jaw bone of a cat found at the Ladds fossil site.  Click to enlarge.  Dr. Clayton Ray thought this specimen was most like the jaw bone of a jaguarundi, but other scientists have concluded it’s from a cat that was more like a margay.  This page is from the below referenced paper authored by Dr. Ray.

Photo of a jaw bone of a cat found at the Isle of Hope site near Savannah, Georgia. Click to enlarge.  Every measurement of this specimen falls within the size range of both margay and jaguarundi.  This means it can’t be conclusively identified.  It’s slightly smaller than most specimens identified as Leopardus amnicola.  Page from the below referenced study authored by Dr. Hulbert.

The ocelot (Leopardus pardalis) is about the size of a bobcat or maybe a little larger is some cases.  Unlike the margay, it’s primarily a ground dweller, though it can climb trees.  It mostly feeds upon rodents.  Today, ocelots range throughout Central and South America and rarely into south Texas and Arizona.  In the 19th century, they were found in Louisiana and Arkansas, and fossil evidence of this cat has been found from 2 sites in Florida, also probably dating to a warm interglacial.

The ocelot and margay shared a common ancestor.  It’s likely that some individuals of this ancestral species preferred hunting on the ground and their decendents evolved into ocelots, while other individuals preferred hunting in the trees and their decendents evolved into margays.  Males that were good tree climbers were more likely to meet females that were good tree climbers, and they passed on the beneficial genes that gave them their natural ability.

The ocelot can grow to a size as heavy as 40 pounds.  Also used to range into southeastern North America.

The jaguarundi (Puma yagaouroundi) is a 3rd species of small neotropical cat.  It was formerly classified in its own genus by some scientists and lumped in the Leopardus genus by others, but genetic studies suggest it is closely related to the cougar (Puma concolor).  I hypothesize that an isolated population of cougars began specializing in small prey to avoid competition with larger carnivores such as jaguars, saber-tooths, and lions.  This population then evolved into jaguarundis.  Studies show cougars regularly take smaller prey than jaguars, and there isn’t much overlap in their prey selection.  In some locality with scarce prey, competition may have forced the ancestral population to take even smaller prey.  Today, the jaguarundi preys upon birds, rodents, opposums, small species of deer (brocket), reptiles, and insects.  It eats fruit as well.  It ranges throughout Central and South America and rarely south Texas.  100 years ago, some were introduced to Florida, and a small population may still exist there.  Reported sightings continue.

The jaguarundi may have ranged into southeastern North America as well.  It’s also known as the otter cat due to its cylindrical shape.  It’s closely related to the cougar but is about 10% its size.

It’s evident at least 2 species of neotropical cats colonized southeastern North America during warm climatic phases of the Pleistocene.  I hypothesize that they continued to live in the region until approximately 28,000 BP.  Dense forests remained widespread in the region until then.  Between ~28,000 BP-~15,000 BP prairies, desert scrub, and spruce woodlands replaced the kinds of forests margays and ocelots prefer, though it’s possible they persisted near the coast where ocean currents kept the climate from deteriorating.  If it wasn’t for man, I think ocelots and margays would have recolonized the south.  Fossils of margays have been found in Texas, and they date to 4400 BP, showing they were more widespread recently.  However, native Americans coveted their beautiful coats, and I suspect human hunters prevented the re-expansion of their range.

References:

Hulbert, Richard; and Ann Pratt

“New Pleistocene (Rancholabrean) Vertebrate Faunas from Coastal Georgia”

Journal of Vertebrate Zoology 18 (2) June 1998

Ray, Clayton

“Pleistocene Mammals from Ladds, Bartow County, Georgia”

Georgia Academy of Science Bulletin 25 (3) 1967