The Largest Saber-toothed Cat, Smilodon populator

Smilodon populator may have been the largest cat ever to have hunted in the wild.  Richard Farina, a South American paleontologist, estimated this species reached a weight of over 800 pounds.  This is more than twice as big as the more famous Smilodon fatalis, a species that lived all across North America during the late Pleistocene.  Smilodon fatalis also ranged into South America west of the Andes Mountains, while S. populator occurred east of this mountain chain.  Apparently, the Andes Mountain chain served as a geographical barrier, resulting in the evolutionary divergence of the 2 species of Smilodon.

Smilodon populator reached an astonishing 800 pounds in weight.

S. populator was an ambush predator that wrestled its prey to the ground and bit its throat, slicing through windpipe and jugular with its long fangs.  Scientists assumed it lived in forested environments where it could more easily surprise its prey from behind cover.  However, a recent study, using isotopic analysis of bone collagen from sub-fossil specimens, determined S. populator and its favorite prey lived in an open dry environment.  According to this study of specimens from 6 different sites in Argentina, S. populator’s favorite prey was macrauchenia, a now extinct primitive ungulate.  Macrauchenia occupied an ecological niche similar to that of a modern day giraffe’s.  With its long neck it could reach tree leaves unavailable to horses and deer, but it also grazed on grass.  S. populator also often preyed upon 2 species of ground sloths–the enormous megatherium and lestodon.  Prey species other than macrauchenia, megatherium, and lestodon made up less than 5% of S. populator’s diet, if this isotopic analysis accurately reflects the big cat’s diet.  Giant ground sloths moved so slowly that S. populator would likely have had no problem seizing an individual.  I suspect they mostly attacked weaned sub-adults, no longer protected by their mothers.  Full grown sloths would have been difficult to subdue because they were large, powerful,  armored under thick skin, and armed with big claws.  Some scientists believe ground sloths dug burrows as a kind of strategy to defend themselves from S. populator.  These burrows still exist.  (See: https://markgelbart.wordpress.com/2012/10/10/some-giant-ground-sloths-dug-long-burrows/ )  A ground sloth in a burrow with its back protected would have been impossible for a Smilodon to kill.

I hypothesize S. populator had a black or dark gray coat that made it difficult to see in the dark.  This allowed them to ambush sleeping macrauchenia in the open.  It explains how a large relatively slow predator could catch a better runner, like macrauchenia. I believe S. populator hunted ground sloths during the day when they left their burrows to feed and sleeping macrauchenia at night when the latter were less alert.

An isotopic study suggests macrauchenia was Smilodon populator’s favorite prey.

An extinct canid, Protocyon trogl0dytes, may have competed with S. populator.  The isotopic values of 1 specimen of this species closely matches those of the many specimens of S. populator analyzed in the study referenced below.  This suggests Protocyon ate the same prey species as S. populator, however, the sample size is too small to reach a definite conclusion about this species diet.  It’s not known whether this species was an active hunter, a scavenger, or both.  Isotopic evidence from a single specimen of a jaguar from the late Pleistocene of South America indicates it preyed on different species–horse, deer, and rodent.

S. populator lived in South America for at least 750,000 years.  It ecologically replaced a saber-toothed relative of the marsupials known as Thylacosmilus atrox.  Smilodon may have outcompeted Thylacosmilus and driven it to extinction.  However, there is a 1 million year gap in the fossil record between the most recent specimen of T. atrox and the earliest specimen of S. populator.  It’s not known for certain whether the 2 species ever overlapped in time.

In the conclusion of the below referenced paper the authors suggest a change from dry open environments to more humid forested conditions may have contributed to the extinction of S. populator.  I strongly disagree with this notion because a) S. populator survived as a species for over 750,000 years of climatic changes and b) dry open environments are still widespread in South America, most notably in the Gran Chaco region.

Smilodon populator hunted in a dry open environment, not dissimilar from this palm savannah in the Gran Chaco region of Argentina.

I’m convinced man is entirely responsible for the extinction of S. populator.  Humans overhunted Smilodon’s favorite prey, depriving the big cat of food, and probably directly hunted the big cats.  Its great size became a disadvantage after man colonized the region because it was an easy target to hit with spears thrown from a great distance.

Reference:

Bocherens, Herve; et. al.

“Paleobiology of Sabretooth Cat Smilodon populator in the Pampean Region (Buenos Aires Province, Argentina) around the Last Glacial Maximum: Insights from Carbon and Nitrogen Stable Isotopes in Bone Collagen”

Paleogeography, Paleoclimatology, and Paleoecology March 2016

Tags: humans responsible of S. populator's extinction, Hypothesis that S. populator had a dark coat, Smilodon populator