New Research Redefines the American Cheetah's Identity and Habitat

New findings from researchers at the University of California, Santa Cruz, are reshaping our understanding of Miracinonyx trumani, often referred to as the American cheetah. Contrary to its name, this extinct predator was not a true cheetah, but rather a flexible relative of the puma that thrived in various environments, including the Arctic, by relying heavily on fish.

Published in the journal Current Biology on September 4, the study reveals that M. trumani inhabited a range extending about 20 degrees of latitude northward, previously unrecognized by scientists. While they acted as versatile generalist predators in temperate regions like Wyoming and Florida, the species adapted to specialized roles in the Arctic, preying primarily on anadromous fish like salmon.

Adult Miracinonyx trumani are estimated to have weighed around 150 pounds, standing roughly three feet tall and measuring about eight feet from head to tail. Although their proportions suggested similarities to modern cheetahs, emerging evidence indicates these cats were much more versatile in their hunting approaches, effectively pursuing prey on land and employing strong forelimbs for catching and holding it.

"These cats displayed remarkable flexibility, much akin to modern pumas," noted Molly Cassatt-Johnstone, Ph.D. candidate in the Paleogenomics Lab at UC Santa Cruz and lead author of the study. Genomic analysis uncovered loss-of-function mutations in specific genes related to circadian rhythms, hinting at their adaptability to the extreme light conditions present during northern summers and winters.

The role of M. trumani in Ice Age North America's ecosystem has been significant in shaping scientific theories. Historically, it was thought that this predator drove the astonishing speed of the American pronghorn through evolutionary pressure.

However, the new genetic data disrupts this narrative. Researchers have placed M. trumani as a sister species to modern pumas, splitting from that lineage about 2.6 million years ago. Its cheetah-like body shape exemplifies evolutionary convergence, where different species independently develop similar traits in response to like environmental challenges.

To explore how this species adapted to radically different habitats, researchers sequenced high-quality genomes from fossils dating back between 23,000 and 31,000 years. The analysis of these genomes revealed traits well-suited for surviving the harsh climatic conditions of the Late Pleistocene.

The fossil specimens studied from Yukon Territory were collected from areas traditionally stewarded by the Tr'ondëk Hwëch'in and Vuntut Gwitchin peoples, recognizing their enduring cultural connection to the land.

A notable genetic finding was the absence of a functional gene responsible for detecting sour tastes, marking a significant sensory adaptation. It's already known that cats lack a penchant for sweet flavors, but this discovery represents the first recorded case in felids of inactivated genes related to sour taste perception. This is often correlated with specialized diets.

Co-author Matthew Wooller, professor at the College of Fisheries and Ocean Sciences at the University of Alaska Fairbanks, stated, "This species showcased a wide range, spanning from the Arctic to the lower 48 states, illustrating extreme specialization across vastly different ecological niches." They managed two distinct food sources at opposite ends of their range.

The results also shed light on the eventual extinction of M. trumani towards the end of the Pleistocene. Researchers identified low genetic diversity among specimens from both Wyoming and Yukon, although there were no signs of severe inbreeding or significant population bottlenecks like those observed in modern pumas. The data suggests a slow, gradual decline from early to late Pleistocene as a potential reason for the scarcity of fossils and the species' vulnerability to extinction.

Senior author Beth Shapiro, a professor specializing in ecology and evolutionary biology at UC Santa Cruz, noted, "Low genetic diversity wasn’t a death knell for this species. Miracinonyx survived a long period without evident inbreeding complications, suggesting that a gradual decline left the species unable to adapt to shifting climatic conditions."

The research serves as a reminder of the pitfalls in identifying extinct species based solely on physical characteristics. The term "American cheetah" misrepresents both its evolutionary ties to true cheetahs and its hunting strategies, which diverged significantly from those predators.

This collaborative effort included researchers from UAF, the Yukon Paleontology Program, and Des Moines University, demonstrating the collective pursuit of understanding ancient wildlife.

Materials provided by University of California - Santa Cruz. Content may be edited for style and length.