To learn how these cheetahs survived, the team applied stable isotope analysis to tiny bone fragments from the animals' paws and legs. Matthew Wooller, director of the Alaska Stable Isotope Facility, oversaw the testing, which can reveal the types of food an animal ate.

The isotope results showed the Yukon cheetahs ate almost only fish, most likely salmon. This diet is highly unusual for felids and contradicts the long‑standing view that American cheetahs chased pronghorn antelope on open plains. Cassatt‑Johnstone noted that pronghorns never lived in Beringia, the region that includes the Yukon.

Further DNA sequencing showed Miracinonyx was genetically closer to North American pumas than to African cheetahs. The study also found very little genetic variation within the population, a factor that Cassatt‑Johnstone says may have helped drive the species to extinction. Because of their unique Arctic lifestyle, Grant Zazula has suggested calling this group the “Yukon Cheetah.”

These findings illustrate how DNA and isotope science can overturn long‑held ideas about extinct predators, revealing that an ice‑age cat adapted to a fish‑rich environment far from the grasslands we imagined.