The 'American Cheetah' Was Not a Cheetah. Its DNA Puts It in the Yukon, Eating Salmon.

For decades the extinct North American cat Miracinonyx trumani has been called the American cheetah, on the strength of a lean skeleton and long legs that look built for running down pronghorn on the western plains. A study published Thursday in Current Biology takes that name apart. Ancient DNA recovered from its remains places it not among cheetahs but as a sister species to the modern puma, the two lineages splitting roughly 2.6 million years ago.

The work comes from the Paleogenomics Lab at the University of California, Santa Cruz, with doctoral candidate Molly Cassatt-Johnstone as lead author. The resemblance to a cheetah turns out to be convergent evolution — two unrelated animals arriving at the same body plan because the same job, running fast in open country, has the same engineering answer.

The bigger surprise is where the animal lived. Specimens in the study extend its confirmed range about 20 degrees of latitude farther north than the fossil record had documented, into Canada's Yukon Territory. That is not marginal territory for a sprinting predator of open grassland. It is the Arctic, with months of darkness and months of near-continuous light.

The genomes suggest the cats adjusted. The northern animals carry loss-of-function mutations in circadian rhythm genes — the internal clock machinery that ties an animal's sleep, hunting and hormone cycles to the day-night cycle. Switching parts of that system off is a plausible adaptation for a predator living where the sun does not set for weeks and then does not rise for weeks.

Their diet also split by geography. Isotopic and genomic evidence indicates the Arctic populations specialized on anadromous fish such as salmon, while animals recovered from Wyoming and Florida behaved as generalist predators. A 150-pound cat, about three feet at the shoulder and eight feet long including the tail, fishing a northern river is not the picture the "American cheetah" label conjures.

The study turned up one more oddity that reaches beyond this species. Every felid the team examined lacked functional genes for sour taste perception — the first recorded instance of that particular sensory loss in cat lineages. Losing a taste receptor is usually a signal that whatever it detected stopped mattering, which points back at diet.

On extinction, the genomes argue against a sudden collapse. The population carried low genetic diversity for thousands of years without the signatures of inbreeding that usually accompany a crash. The picture is of a species that had been thinning slowly for a long time, and that had no reserve left when the climate shifted at the end of the last Ice Age and the megafauna it lived alongside disappeared.