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

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Cougars, House Cats, and Berserkers

Cougars are capable of breeding year round.  This is evidence they evolved from an ancestor that lived in a tropical climate.  Other large mammals living in temperate climates breed in late fall and early winter so they can give birth in spring and early summer when food is more abundant.   Deer and elk fawns and bison calves build a layer of fat during summer that helps them survive harsh winters.  But the same isn’t true for cougars.  Cougars give birth year round, and scientists have found no difference in survival rates among kittens born during different times of the year.  A kitten born during a harsh winter in the Rocky Mountains even has some advantages.  The mother doesn’t have to travel as far to find food because there is an increase in the number of prey animals weakened from starvation.  Animals such as elk and deer also struggle in deep snows, making them easier to kill.  Moreover, bears, a dangerous threat to kittens left alone by hunting mothers, are hibernating and not foraging.  There was no advantage for cougars to evolve the trait of breeding only during certain times of the year. Photo from the December 1994 issue of Natural History Magazine showing a cougar killing a mountain goat. The illustration of the larger cat is an artist’s rendering of the middle Pleistocene cheetah–Miracinonyx inexpectus.  The smaller cat in the picture is a modern day cheetah.  Cougars evolved from the ancestor of the middle Pleistocene cheetah, known as Studer’s cheetah–Miracinonyx studeri.  Studer’s cheetah had characteristics intermediate between a cougar and a cheetah.  It could run faster than a cougar, but was larger, stronger, and more powerfully built than a modern cheetah, and therefore could climb trees and ambush larger prey.  North American cheetahs had retractible claws, a characteristic modern cheetahs lack. Cougars were a common predator in the southeast during the late Pleistocene.  There is plenty of fossil evidence of cougars from Georgia and Florida.  Fossil evidence of cheetahs comes from middle Pleistocene sites in Florida, but by the late Pleistocene American cheetahs were restricted to the western part of the continent. The biggest threat to cougar kittens is adult male cougars.  There is an evolutionary advantage for male cougars that kill cougar kittens.  Male cougars that kill the offspring of other males can then mate with the females that go into heat following the loss of their kittens.  This increases the chance his genes will continue into the future.  A male cougar that covers the most territory, kills the most kittens, and mates the most often is generally the fittest, most capable individual in the area.  Baby-killing appears to be a universal trait among most, if not all, cat species, including the house cat (Felis domestica). Lone Ranger, my favorite cat.  She was the runt of a litter.  She adopted me during the dead of winter about 2.5 years ago.  Despite her small size, she bravely drives off the much larger tom cats who try to kill her kittens.  Nevertheless, she has never successfully protected her kittens from the persistent homicidal males for longer than 6 weeks.  Oddly enough, she willingly mates with the tom cats days after they kill her babies. Currently, two female cats have adopted my yard as their home base.  Hissy-fit was one of a whole slew of cats that I think belonged to a former neighbor two houses from mine.  The underfed, half-feral cats swarmed to my compost pile whenever I threw junk in there they considered edible.  I began to pick favorites from this group and fed them real food.  Eventually, cars, dogs, and disease thinned the number of cats, but Hissy-fit, my least favorite, still lives.  She is not a friendly cat–she hisses at me, and she used to lean away (a hint not to pet her) even as I fed her, though after several years of socialization, she now tolerates being petted.  She rarely makes the meow vocalization, but instead hisses, even when she’s seemingly not angry.  She gave birth to my favorite cat–Lone Ranger, the lone survivor from that litter.  She left Lone Ranger for long periods of time on our front door step one cold December when the kitten was a few weeks old.  I took the time to properly tame her, and the first time I let her play with a ball of yarn, she purred.  Lone Ranger is a gentle, affectionate cat, but she is a slut.  In 2 1/2 years she’s already had 3 litters.  Despite being a runt, she’s always very courageous when defending her kittens from the much larger tom cats that persistently try to kill every kitten in their territory.  When she’s protecting her own kittens, she even drives her own mother from the yard.  Hissy-fit just gave birth to another kitten, and Lone Ranger is helping her defend it.  The two cats worked as a team to defend a single newborn kitten last summer as well but were ultimately unsuccessful.  Tom cats are relentless and merciless. I noticed a peculiarity last year.  Lone Ranger went into heat and mated with a tom cat I suspected of killing and eating her kittens a few days earlier.  Imagine if a human mother would agree to have sex with a man who killed and ate her babies.  It seems unthinkable, bizarre.  Yet, in human history similar scenarios are not that uncommon.   Vikings, aided by a berserker, raiding a village.  Berserkers were psychotically violent  men used as shock troops.  In peacetime they were bullies who challenged rich men to death duels.  After killing the wealthy man they took his land, livestock, and women.  Geneological records show berserkers did leave more descendents than other men.  Humans are not so different from cats afterall. The Vikings were known for their violent culture, but within this society were men who were the most violent of the violent–the creme` de la creme`, so to speak.  These insanely violent men were called berserkers.  Historians suspect they may have been psychopaths or schizoids immune to any semblence of conscience.  Viking kings used them to help intimidate the monasteries and villages they raided and looted.  Berserkers were a great help when they were on a raid, but at home during peaceful intervals they posed a problem.  They often challenged rich men to death duels.  I doubt wealthy men really had a viable way of opting out.  After killing the wealthy man, the berserker confiscated his land, livestock, and women.  The Vikings considered women little more than livestock.  The Viking wives and concubines had no choice but to submit to sex with the psycho who murdered the man they probably loved.  Berserkers were probably indifferent to the fate of babies and toddlers, but I’m sure infanticide did happen.  Berserkers infamously killed people who disturbed their sleep, and crying babies will do that. Incidentally, I don’t think many of the hundreds of google images of berserkers are historically accurate.  They’re always depicted as uber-muscular giants.  I believe berserkers were ordinary looking men.  It doesn’t take much muscle to kill a man with a sword or battle axe.  Instead, it takes ferocity and a lack of inhibition to murder.  The inhibition against killing other human beings is so surprisingly strong, that military experts extimate only 15% of U.S. combat infantrymen fired their rifles during World War II, even when they were being attacked.  The modern military specially trains men to overcome this inhibition, but still only achieve a 90% success rate at getting combat infantrymen to fire their weapons against other human beings in combat. Vikings were not the only culture that approved of killing other men and taking their women.  Many American Indian tribes massacred enemy villages with the exception of breeding-age women which they enslaved.  The Mongols under Ghengis Khan wiped out men and spread their seed among the surviving women to such an extent that today a significant percentage of the population in Eurasia has Mongol ancestry.  Some South Pacific Islanders not only killed their enemies but ate them as well.  Cannibalism most frequently occurs on crowded islands where there is a shortage of big game animals, and the people get tired of eating fish.  Overcrowded environments are also a contributing factor.  Perhaps, if overpopulation of the world approaches that of South Pacific islands, cannibalism might become as common for humans as it is for cats.  Maybe the movie, Soylent Green (based on the book, More Room, More Room) was a prophecy. Reference: McAllister, Peter Manthropology St. Martin’s Press 2009