UW Researchers Contribute to Two Papers that Show Mountain Lions Genetic Connectivity Dangerously Low

University of Wyoming researchers contributed to two research papers that focus on the conservation of a dangerously inbred mountain lion population in Southern California.

If this population is to survive in the future, an urgent need for genetic connectivity must be met, according to two scientific papers from a team of researchers coordinated by the University of California-Davis and involving scientists from UW and the University of Massachusetts–Amherst.

The first paper, titled “A Single Migrant Enhances the Genetic Diversity of an Inbred Puma Population,” was published in Royal Society Open Science May 24. The journal publishes high-quality research across all of science, engineering and mathematics.

That study reports that the puma population of approximately 20 adults in the Santa Ana Mountains has the lowest genetic diversity ever reported for pumas besides the Florida panther, which nearly went extinct from genetic causes.

The pumas’ isolation is primarily due to surrounding urbanization from Los Angeles and San Diego.

“The only hope for puma movements in and out of the Santa Ana Mountains is to cross I-15 -- an eight- to 10-lane interstate highway -- which poses a major barrier for pumas attempting to migrate between the Santa Ana Mountains and the rural Eastern Peninsular Mountains,” says lead author Kyle Gustafson, a postdoctoral conservation geneticist from UW. 

UW researchers conducted genetic analyses of both radio-collared and uncollared pumas to develop a multigeneration pedigree. This showed where pumas and their offspring were born, and whether they successfully migrated and reproduced after crossing the I-15, which separates the Santa Ana Mountains from other mountain ranges to the east.

The Power of One Puma

Although seven males crossed I-15 over the past 20 years, only one -- referred to as male puma #86 or M86 -- was able to successfully produce offspring in the Santa Anas after migrating from the genetically diverse population to the east. By producing a total of 11 detected offspring, M86 rapidly disseminated unique genes into the inbred population, which reduced the level of inbreeding and significantly increased genetic diversity.

Senior author Holly Ernest, a wildlife population geneticist and research veterinarian at UW, says that, by introducing new genetic material and raising the level of genetic diversity in this population, that single male mountain lion, M86, performed what amounts to a “genetic rescue.”

“Our study also shows how quickly his genetics were lost by high mortality levels of his offspring,” says Ernest, the Wyoming Excellence Chair in Disease Ecology. “A message here is that this population needs help to regain healthy genetics and persist in the Southern California landscape. That help can come in the form of just a few individuals over time adding ‘new blood’ to the population.”

Unfortunately, M86 was hit by a car between 2014 and 2015, and more than half of his offspring are either now deceased or in captivity.

“This is consistent with mortality rates we found previously in the region,” says Winston Vickers, a wildlife veterinarian from UC-Davis’s Karen C. Drayer Wildlife Health Center, who conducted most of the field research. “Only one other migrant, named M119, remains in the Santa Ana Mountains, but whether he is alive or produced offspring is uncertain.”

Connectivity Is Key to Conservation

The second paper, titled “Multi-Level, Multi-Scale Resource Selection Functions and Resistance Surfaces for Conservation Planning: Pumas as a Case Study,” and published June 13 in the journal PLOS ONE, provides a potential solution to this issue. PLOS ONE provides a platform to publish primary research, including interdisciplinary and replication studies as well as negative results.

In it, the researchers, including Ernest, who was a co-author, propose a conservation network for pumas spanning the Santa Ana Mountains and the Eastern Peninsular Mountains.

Using genetic data and data from GPS radio-collared pumas, this analysis identified critical habitat patches, movement corridors and key road crossing locations across I-15 that would allow pumas to persist and increase genetic diversity.

“Without continued emigration into the Santa Ana Mountains by pumas coming from the east of I-15, eroding genetic diversity and continued inbreeding are expected to resume,” says veterinarian Walter Boyce, co-director of the Wildlife Health Center’s Southern California mountain lion study with Vickers.

Protected areas in Southern California currently cover about 50 percent of this proposed puma conservation network. Incorporating key new areas in Orange, Riverside and San Diego counties would increase the protected areas to nearly 80 percent. Habitat protection, coupled with wildlife crossing structures and wildlife fencing, will be needed to promote the safe passage of pumas across I-15 and ensure adequate gene flow.

“The current protected area system is not enough to ensure the survival of pumas in Southern California,” says lead author Katherine Zeller, a wildlife biologist at the University of Massachusetts-Amherst. “Without additional avenues for pumas to move safely between large habitat blocks, these populations will continue to see decreased gene flow, as well as high mortality rates, which will decrease their chances of long-term survival in the region.” 

Primary financial support for the research was provided by the San Diego County Association of Governments, and the California Department of Fish and Wildlife. The studies required partnerships across research institutions and state agencies to combine GPS and ecological data collected over 15 years by researchers with the UC-Davis Southern California mountain lion study with analysis of genetic, habitat use and movement data by researchers at UW and University of Massachusetts-Amherst.