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Davis, California

Monday, April 15, 2024

Safer passages to relieve genetic pressure needed for California mountain lions

Mountain lion F92 and her kittens dining. F92 is a partner and daughter of M86, a male mountain lion who crossed I-15 and relieved some genetic pressure in the Santa Ana populations. (THE WILDLIFE HEALTH CENTER SOUTHERN CALIFORNIA MOUNTAIN LION PROJECT / COURTESY)

Researchers provide genetic evidence for conservation policy change

A 2017 paper published by the Royal Society described the genetic diversity of mountain lions in Southern California and suggests methods to conserve their space for protection. A team of University of Wyoming and UC Davis scientists analyzed biological samples of mountain lions collected near Los Angeles and San Diego since 2001 to create a genetic structure and pedigree of the populations.

Mountain lions, also called pumas or cougars, are large cats living in the forests and mountain ranges of the Americas. Pumas serve as apex predators in their habitats, hunting most other moving animals, especially deer and small mammals. Cougars, particularly the males, roam in large areas and live in solitude until seeking partners for mating. About 5,000 pumas live in California.

Pumas living in Southern California have been dealing with human developments intruding into their habitats in recent years. A particular problem has been Interstate Highway 15, which sliced a mountain lion habitat in half, leaving the Santa Ana mountain lion population vulnerable to inbreeding. The fragmented habitat reduces the ability of the felines to freely move, mate and create new offspring.

Kyle Gustafson is a postdoctoral conservation geneticist in Dr. Holly Ernest’s Wildlife Genomics and Disease Ecology Laboratory at the University of Wyoming. Gustafson was in charge of the data analyses and writing the research paper. Mountain lions are named in this project by their sex (M for male, F for female) along with an identifying number.

“Although 7 males have crossed I-15 over the last 15 years, only a single male (named M86) was successful at mating,” Gustafson said. “He sired 11 offspring, reduced inbreeding and increased the genetic diversity of the Santa Ana population.”

The pumas on the Santa Ana side have become significantly inbred due to difficulty mating with the more diverse mountain lions in the Eastern Peninsular Range across the highway. The bright lights and noises from vehicles and human activity near the freeway disturb animals who wish to cross.

“Overall, mountain lions are doing well in California,” said Patrick Huber, a conservation scientist at UC Davis who researches land use plans for animals such as mountain lions but was not involved in this project. “It’s these specific populations we are worried about”.  

UC Davis researchers have been trapping pumas to affix them with tracking collars for years. Monitoring where mountain lions travel helps scientists understand their range and how cougars move between populations in their lifetimes. Scientists detected M86 crossing I-15 in 2010 from the Eastern Peninsular Range to the inbred Santa Ana mountain lion population because of a tracking collar.

Dr. Winston Vickers is a wildlife veterinarian at the Karen C. Drayer Wildlife Health Center at UC Davis and has been involved with mountain lion research at least 15 years. Vickers has extensive experience trapping and collaring pumas in the field and is one of the authors of the paper.

“The males are the critical element to spreading genes through the landscape,” Vickers said.

Tissue samples of 146 animals were used to create a genetic structure of the mountain lion population. Gustafson’s analyses concluded that mountain lion M86 significantly improved the genetic metrics of the Santa Ana population over a few years with an infusion of diverse genes through its offspring. Allelic richness increased in the samples Gustafson investigated.

“Pumas in the Santa Ana Mountains and Eastern Peninsular Range, which are biologically capable of traveling for miles, are being inhibited from mating by I-15, which is only 8-10 lanes,” Gustafson said. “Essentially, we are finding distinct populations on either side of I-15, which is only the length of a football field. This is highly surprising based on the fact that pumas have been documented to cross major areas, including the entire Central Valley of California.”

M86 was killed by a vehicle after contributing some new genetic material to the Santa Ana mountain lion population. Another puma who successfully crossed the highway to the Santa Ana side was legally shot and killed before mating due to preying on domestic animals.

“Over time, we discovered, through following them around, these animals had shorter lives and worse mortality rates than we had imagined,” Vickers said.

Most mountain lions die due to car strikes from crossing interstate highways. Male mountain lions roam far between populations to mate, which helps to keep genetic diversity among groups at reasonable levels. Creating healthy offspring strengthens the local populations, but males journeying across highways such as I-15 or I-10 don’t always make it across alive. Vehicle strikes not only kill large and important animals, but contribute to human fatalities and millions of dollars in property damages every year.

Pumas are also threatened by humans with firearms. Californians can apply for permits to kill mountain lions if livestock or pets are attacked. Last year, over 100 mountain lions were killed by depredation permits issued by the state. Changes in animal husbandry tactics could prevent mountain lions from preying on domestic animals.

“Concerned citizens could be cautious of pumas while driving and keep their domestic animals protected from any potentially hungry pumas,” Gustafson said.

Creating safe ways for animals to cross over or under freeways and away from human developments is one way to reduce the impact of habitat alteration on genetic diversity. Erecting a green passage over a highway for mountain lions could improve travel for other species, such as bear and deer, who also fall victim to vehicle strikes.

“People are getting creative about certain types of crossing structures,” Huber said.

An area just south of Temecula is a prime location for a wildlife corridor to connect the Santa Ana and Eastern Peninsular Range mountain lions over I-15, but funding for the project is uncertain. Another project to the west near Liberty Canyon would cross US 101, allowing the Santa Ana pumas to travel north more safely, but would probably not improve genetic diversity as much as the Eastern Peninsular corridor. Funding for the Liberty Canyon Wildlife Crossing is more optimistic due to local philanthropists and nonprofit organizations such as the National Wildlife Federation. The estimated costs of the Liberty Canyon project, including construction and land purchases, would be $57 million.

“The National Wildlife Federation has committed to raising a large amount of money to create a crossing, so it’ll be privately funded,” Huber said.

The genetic pedigree created using 15 years of blood and tissue samples from multiple generations of California cougars gives a status update on how the felines are faring in their fractured habitat. The research collected over several years gathered data from many animals who were trapped, tracked and sampled with follow-up visits.

“An underappreciated difficulty is the establishment of long-term ecological studies,” Gustafson said. “This study spanned nearly 20 years. Without this long-term data, our ability to understand these populations and individuals would be extremely limited.”

Data from long-term studies is more convincing than cross-sectional studies at one point in time. Policy updates can help conserve and connect mountain lion territory while cutting down on the economic burdens of vehicle strikes and domestic predation.

“Citizens can be active politically in supporting fiscal policy which takes into account wildlife needs,” Vickers said.


Written by: George Ugartemendia — science@theaggie.org


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