Study: Mountain Lions in Southern California Lack Genetic Diversity

The study, led by the University of California, Davis, in partnership with The Nature Conservancy, raises concerns about the status of mountain lions in the Santa Ana and Santa Monica mountains.

This female mountain lion, known as F52, was collared in the middle portion of the Santa Ana range. She later died near a busy highway of unknown causes. Mountain lions in the Santa Ana range are effectively cut off from those on the other side of I-15, which strongly contributes to their genetic decay, a U.C. Davis study found.

U.C. Davis

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Mountain lions in Southern California are facing a severe loss of genetic diversity, according to a new study by the University of California, Davis, and The Nature Conservancy. Research points to human development and freeways as the culprit.

The study was published Oct. 8 in the journal PLOS ONE.

Scientists collected and analyzed DNA samples from 354 mountain lions statewide, including 97 from Southern California. Mountain lions in the Santa Ana Mountains displayed lower genetic diversity than those from nearly every other region in the state.

The Santa Ana Mountain range, located south of Los Angeles and north of San Diego, is surrounded by urbanization and a growing population of about 20 million people, according to U.C. Davis. A small habitat linkage to the southeast connects the mountain lions to the Peninsular Range, but it is bisected by Interstate 15—a busy 10-lane highway—and associated human development, the school noted. The study highlights the urgency to maintain and enhance the little connectivity remaining for coastal mountain lions, especially across I-15.

The mountain lions have also recently gone through a “population bottleneck,” according to the study. This means that the mountain lion population size has decreased sharply to a fraction of its original size.

“The genetic samples give us a clear indication that there was a genetic bottleneck in the last 80 or so years,” said lead author Holly Ernest, DVM, Ph.D., who, at the time of the study, was a professor with the Karen C. Drayer Wildlife Health Center and the Veterinary Genetic Laboratory at U.C. Davis. She is now a professor at the University of Wyoming. “That tells us it’s not just natural factors causing this loss of genetic diversity. It’s us—people—impacting these environments.”

Southern California mountain lions are also threatened by habitat loss and fragmentation, and death from various causes such as vehicles, depredation permits, poaching, disease, public safety kills, wildfire and poisoning. An elevated combination of these factors could be a tipping point for the population, according to U.C. Davis.

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U.C. Davis/The Nature Conservancy

This map identifies mountain lion captures in the Santa Ana Mountains and eastern Peninsular ranges of southern California. The colors of symbols represent different genetic groups, illustrating barriers to gene flow. Busy highways and growing urbanization in the area threaten mountain lions and have led to their genetic decay, according to U.C. Davis.

However, it’s not too late to protect the region’s mountain lions, according to Ernest.

“I think there could be hope for this population,” she said. “They’re at a point where they can be monitored and protected.”

Possible measures could include protecting migration corridors and some lands slated for development that could connect the Santa Anas to areas in the east, as well as strategically installing protective corridors for the mountain lions to navigate busy highways.

The work received funding from the California State Parks, California Department of Fish and Wildlife, The Nature Conservancy, The McBeth Foundation, Anza-Borrego Foundation, Nature Reserve of Orange County, National Science Foundation and private donors. The Nature Conservancy and California Department of Fish and Wildlife helped with sample and data collection.

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