Dead Mountain Lion Shows Highways Turning Santa Monica Mountains NRA Into Genetic Island

The area surrounding the Liberty Canyon exit on the 101 Freeway is an ideal location for a wildlife crossing because it has natural habitat on both sides of the freeway and connects to vast areas of open space. NPS photo.

Bottled-up genetics lead to problems, as evidenced by the inbreeding woes of the wolves at Isle Royale National Park. Though mountain lions that roam Santa Monica Mountains National Recreation Area in California aren't as inbred as those wolves, the lack of genetic diversity is a growing concern.

That's why the loss last month of a male lion heading towards the NRA was so great, and why it renewed calls for building wildlife tunnels beneath highways that ring the NRA.

Preliminary DNA results from the mountain lion killed on the 101 Freeway in Agoura Hills indicate the lion was traveling from the north and was on the verge of bringing new genetic material to the isolated population in the Santa Monica Mountains, park officials said.

"The fact that this young male chose to cross – unsuccessfully – at Liberty Canyon shows how critical this wildlife corridor is for maintaining genetic diversity in the Santa Monica Mountains," said Dr. Seth Riley, an expert on urban wildlife with Santa Monica Mountains National Recreation Area. "This section of the 101 Freeway is the ideal path into the Santa Monica Mountains because of the natural habitat on both sides of the freeway and the connections to large areas of open space."

Wildlife advocates have long pushed for a wildlife tunnel crossing near the Liberty Canyon exit where this lion was struck and killed by a car. Caltrans has twice come up short in applying for federal transportation funding for the $10 million project. Another round of applications is expected early next year.

Lions from the Santa Monica Mountains are hemmed in by freeways, the Pacific Ocean and the Oxnard agricultural plain, making the lack of genetic diversity a serious threat to their long-term survival, according to NRA biologists.

Working with the Robert Wayne Lab at UCLA and the Holly Ernest Lab at UC Davis, Dr. Riley and his colleagues have documented genetic differences in populations north and south of the 101 Freeway, as well as multiple cases of first-order inbreeding in which a father mates with his offspring.

Of more than 30 lions tracked during the decade-long National Park Service study, only one has successfully crossed the 101 Freeway. If this most recent lion had successfully crossed and mated, he would have brought new genetic material to the population south of the freeway, park officials say.