DNA Reveals the Extinct ‘American Cheetah’ Wasn’t Actually a Cheetah

Many scientists have long suspected there was something fishy about Miracinonyx trumani, the extinct so-called “American cheetah.” 

It was first identified in the 1970s as a close relative to the cheetahs found in Asia and Africa today because of its slender build, elongated forelimbs, and enlarged nasal cavities. Those features likely allowed it to run fast, though probably not as fast as modern cheetahs. A genetic analysis in 2005 already suggested it was not a cheetah, as did some anatomical differences.

Now, a new study examining four fossils of the extinct cat from the Yukon and Wyoming has reached a similar, definitive conclusion: the American cheetah was no cheetah.

“Trying to understand the evolution, the behavior, the ecology of a species from the shape of their physical remains is a really, really hard task,” says Molly Cassatt-Johnstone, a graduate student at the Paleogenomics Lab at the University of California, Santa Cruz, and lead author of the study. By sequencing the species' DNA and analyzing the chemical composition of its remains, the new study makes a giant leap ahead.

(Cheetah mummies found in Arabian caves provide rare genome from a lost population)

When the researchers used the DNA to construct a feline family tree, the four “American cheetahs” didn’t end up anywhere near African or Asiatic cheetahs. As cheetah-like as their fossilized remains may have looked, their DNA places them closer to the branch of the American puma, also known as the cougar or mountain lion. It also shows that the two are sister species that shared a common ancestor until about 2.6 million years ago.

That timing coincides with a period of rapid cooling on the continent, during which grasslands expanded rapidly. The cheetah-like features that gave M. trumani its pet name may have helped it survive on these plains by outrunning its prey and the larger predators it would have been wise to avoid. The Yukon bones, which were about 30,000 years old, show this North American feline lived as far north as the Arctic.

“This study is the first published record of Miracinonyx in Canada,” says National Geographic Explorer Julie Meachen, a functional morphologist and paleoecologist at Des Moines University in Iowa and a coauthor of the study. She led the 2014 expedition that found several specimens in Wyoming's Natural Trap Cave. "It shows this extinct species could survive in various habitats and was eating very different things in different places."

The team published their findings Friday in the journal Current Biology.

“The major conclusion that Miracinonyx and pumas were sister species seems plausible,” says Stephen O’Brien, a molecular biologist who produced an earlier construction of the felid family tree but was not involved in the recent work. He adds that it is common for genetic evidence from fossils to result in such revisions. “We are regularly correcting evolutionary conclusions that were based on anatomical interpretations.”

Ice Fishing

The discovery that M. trumani  lived across such a wide region left the researchers wondering what it ate. To find out, they analyzed the relative amounts of different forms of nitrogen and carbon in the fossils, which vary with diet. The results from the Wyoming bones, which were about 20,000 years old, resemble those of other predators of the time that fed on herbivores such assuch as pronghorn, horses, bison, and bighorn sheep. But the fossils from the Yukon revealed markedly different chemical values, suggesting a diet rich in fish such as salmon or trout.

Specializing in fish would have been a way for the slender cat to survive in the harsh Arctic climate while avoiding competition with much larger predators like cave lions.

Cassatt-Johnstone notes an interesting difference between cheetahs and Miracinonyx that would have been helpful in catching fish. "Cheetahs have anatomical adaptations in their forearms and wrists that give them extra stability for when they're running really fast,” she says. "But that comes at a trade-off, where they have less flexibility and can't grapple prey the way other big cats do. Miracinonyx did have this ability"

Ross Barnett, an independent researcher who led the 2005 genetic study but was not involved in this work, praised the paper. “To find two populations of the same species with such different diets is really cool,” he says. “That they were found in Arctic biomes is a huge finding.”

(Pumas came back to Patagonia—and met penguins. What happened next surprised scientists.)

Harshad Karandikar, the conservation director of the WCS Papua New Guinea, who previously studied puma diet, points out that pumas are quite similar in having such a wide range and eating a wide diversity of things, and “they extend further all through the tropics.”

The genome also revealed another possible adaptation to life up north, where days are very long in summer and very short in winter: at least two biological clock genes appear to have been disabled in M. trumani, potentially allowing it to be a bit more relaxed about when to roam and when to rest.

Another gene that seems to have stopped working was one that plays a role in the perception of sour taste, adds Cassatt-Johnstone.

“That one surprised me,” she says. “Why would this cat lose this gene for sour taste?”

But when she examined all the other cats she had included in the genetic analysis that allowed her to reconstruct the family tree—from closely related pumas to distantly related lions—she found that they all had mutations that render this gene ineffective.

“This implies it happened millions of years ago," she says, "but it seems no one had noticed yet.”