The American "Cheetah" Redefined: Insights into Miracinonyx trumani

Recent research from the University of California, Santa Cruz, challenges traditional perceptions of Miracinonyx trumani, commonly referred to as the American cheetah. New evidence from paleogenomic studies and isotopic analyses indicates that this prehistoric predator wasn't a true cheetah at all, but rather a close relative of the modern puma. Interestingly, northern populations adapted to harsh Arctic conditions, with diets possibly focusing on fish.

Published in Current Biology on September 4, the study reveals that the known range of M. trumani extends about 20 degrees farther north than earlier scholars suggested. While these cats functioned as opportunistic predators in temperate regions like Wyoming and Florida, they played a distinct ecological role in the Arctic Yukon, likely preying on fish such as salmon.

Adopting a sleek physique, adult M. trumani weighed around 150 pounds, stood about 3 feet tall, and measured roughly 8 feet from head to tail. Though resembling modern cheetahs, their anatomy suggests a more versatile hunting style. This species appears to have been capable of both land pursuits and adeptly capturing prey with their powerful forelimbs.

Molly Cassatt-Johnstone, a Ph.D. candidate at UC Santa Cruz and lead author of the paper, noted their flexibility, comparing it to that of modern pumas. Genetic analysis pointed to loss-of-function mutations in genes regulating circadian rhythms, hinting at adaptations to the extreme variations in daylight characteristic of northern climates.

Historically, M. trumani played a critical role in explaining the speed of the American pronghorn. Under the "ghosts of predators past" hypothesis, the speed of pronghorns was attributed to their evolution alongside a cheetah-like predator skilled in high-speed chases. However, the latest genomic findings fundamentally shift this narrative.

Researchers have determined that M. trumani is a sister species to modern pumas, having diverged roughly 2.6 million years ago. Their “cheetah-like” appearance is an example of evolutionary convergence, where unrelated species evolve similar traits in response to comparable environmental challenges.

The study involved high-coverage genome sequencing from fossils dated between 23,000 and 31,000 years old. This analysis unveiled genetic adaptations that enabled northern populations to thrive in the challenging conditions of the Late Pleistocene.

Notably, the fossil specimens analyzed in this research originated from Yukon Territory, where respect for the Traditional Territories of the Tr'ondëk Hwëch'in and Vuntut Gwitchin was upheld.

An intriguing aspect uncovered by the genetic analysis includes an unusual sensory trait: both M. trumani and other sampled felid lineages lacked a functional gene that produces a receptor for detecting sour tastes. While felids are typically known for their preference against sweet flavors, this finding is unprecedented in the context of sour taste perception, indicating that specific dietary niches may have influenced these sensory losses.

Matthew Wooller, a professor at the University of Alaska Fairbanks and a co-author on the study, commented on the remarkable range of the species from the Arctic to the contiguous U.S., emphasizing their dual specialization in vastly different environments.

The genetic data sheds light on the eventual extinction of M. trumani at the end of the Pleistocene. Researchers noted low genetic diversity in specimens from both Wyoming and the Yukon, which differs from the severe inbreeding seen in modern pumas. Instead, the evidence points to a gradual decline from early to late Pleistocene, suggesting that this slow decrease in genetic diversity may have rendered them increasingly susceptible to extinction during climatic shifts.

Senior author Beth Shapiro, an ecology and evolutionary biology professor at UC Santa Cruz, highlighted that the absence of signs typical of impending collapse suggests that this decline may have left the species ill-equipped to adapt to changing conditions.

These findings emphasize the importance of caution when labeling extinct species based solely on physical characteristics. By mischaracterizing M. trumani as an American "cheetah," it not only implies a closer evolutionary relationship with true cheetahs but also portrays a misleadingly specialized hunting strategy.

The research results emerged from a collaborative effort that included contributions from the University of Alaska Fairbanks, the Yukon Palaeontology Program, and Des Moines University.

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