Why L.A.'s Mountain Lions Could Soon Vanish

A female mountain lion in the Verdugo Mountains above Glendale
A female mountain lion in the Verdugo Mountains above Glendale

One of the reasons Los Angeles is such a wondrous place is its proximity to nature. Some deserted mountain roads are closer than the average commute; the Pacific brings sharks, string rays and dolphins close to shore; and coyotes and mountain lions are familiar sights even in some of the densest urban neighborhoods in America.

So it's a bummer to learn that one of those icons of L.A. fauna could vanish. Soon.

A new study from researchers at UCLA, UC Davis, Utah State University and the National Park Service says the local mountain lion population could become extinct within 15 years — possibly sooner. 

The reason is that they're trapped by our freeway system. This lack of biodiversity creates "inbreeding depression," a phenomenon by which a population over time loses genetic advantages needed to survive. "Over time a population mating between close relatives will closely erode genetics in a negative way," said Seth Riley, a UCLA professor and park service ecologist who's the study's senior author.

Our small population of mountain lions is trapped above the 101 freeway near Calabasas (see a map, below) and thus has essentially been inbreeding, researchers say. Park service researchers have examined about 50 mountain lions in the region since 1996.

The research, published this week in the journal Proceedings of the Royal Society B, concludes that if nothing changes, our cougars will be wiped out within 50 years, but likely sooner.

"If inbreeding depression occurs in the Santa Monica Mountains population, the model predicted a 99.7 percent chance of extinction within 50 years, with a median time to extinction of just 15 years," according to a National Park Service summary.

That median time means that extinction is possible even sooner than that. Mountain lions have not been designated as an endangered or threatened species, but California lists them as a "specially protected species," which means they cannot be hunted or killed without special permission from the state.

"The interesting thing about the Santa Monica Mountains mountain lions is that they are currently doing well," Riley said. "They survive and reproduce quite well. The problem is over time, they're likely to lose so much of their genetic diversity that survival may suffer."

There is a possible savior on the horizon, however. A $30 million "wildlife passage" over the 101 freeway in Agoura Hills is under consideration. Just such a single bridge, which could connect cougars with mates outside their neighborhood (and outside their families) could save the local species, Riley said. "The science we did supports having a highway crossing," he said.

Caltrans has drafted some rough ideas for the proposed crossing, and the nonprofit Save LA Cougars is raising money to make it happen. Is it worth it to preserve these top cats of the local predatory landscape?

"Mountain lions are an indication that we can maintain a healthy ecosystem in a human-dominated area," Riley said. "If we can protect the largest wildcat in North America in the second largest city in the United States, we can pull this off in other areas where humans dominate."

The proposed wildlife crossing
The proposed wildlife crossing
Caltrans
A map of the wildlife crossing area
A map of the wildlife crossing area

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