L.A.'s Mountain Lions Can Survive, If They Can Cross The 101

A male mountain lion called P-12 was first tagged by National Park Service researchers in Simi Valley. Sometime later, according to movement data broadcast from his GPS collar, he survived crossing Highway 101 and entered the Santa Monica Mountains near Liberty Canyon. 

Likely shaken by his perilous journey, P-12 persevered. He found a nice girl by the name of P-13. After a brief courtship, the two would go on to produce nine offspring. 

One was killed by a car. One died from poisoning. Two were abandoned, presumably because they were runts. Another simply disappeared. Still, by some measure P-12 became quite a successful parent. 

By breeding with a Santa Monica native, the immigrant P-12 introduced much-needed new genes into the local population. To date, P-12 is the only mountain lion to have successfully crossed either the 101 or the 405. (The famous P-22 of Griffith Park of course crossed both freeways, but his crossing isn't technically considered a "success" since he appears fated to be a lifelong bachelor.)

Things started to change when P-12 caught the eyes of P-19, one of his own daughters. Twice. The father and daughter produced five kittens in two separate litters, making P-12 both their father and their grandfather. The lion lothario would go on to breed with another of his daughters, as well as one of his granddaughters. 

In the mountains of Los Angeles just a short drive (depending on traffic) from the studios of Hollywood, an incestuous wildlands drama only suitable for late night premium cable television audiences continues to play out.

It's not just a juicy story, uttered in hushed tones among wildlife biologists over drinks at happy hour. This sordid tale reveals a darker truth. Roads can lead to extinction.

Because the mountain lions of the Santa Monica Mountains are physically isolated from their counterparts in the Angeles National Forest, the Simi Hills, and Los Padres National Forest, they run the risk of becoming genetically isolated as well. Without new mates, the lions wind up mating with their own kin. If that happens too often, the lions start experiencing health problems. Researchers say that they have not yet seen visible signs of inbreeding-related problems in these lions, but it's only a matter of time.

Given how rarely the Santa Monica lion population enjoys an influx of new genes – it's happened just the one time in fifteen years that researchers have been studying the cats – a group of biologists from the National Park Service, UCLA, UC Davis, and Utah State University wanted to find out just how bad things could get, genetically speaking, and how fast. So they created a mathematical model that predicted the future viability of the population. They published their findings this week in the journal Proceedings of the Royal Society: B.

Despite having to contend with a patchwork quilt of land uses and roads crisscrossing the mountains, our lions can maintain a stable population with healthy rates of reproduction. "It shows that the habitat we do have in the Santa Monicas is good. There seems to be enough deer to eat, they're finding each other and reproducing, and raising kittens," says National Park Service wildlife biologist Seth Riley, who oversaw the research. 

"But the Santa Monicas just aren't big enough," he adds. Based solely upon the small size of the habitat, there's a 15-22 percent chance that Los Angeles will no longer be home to as charismatic an animal as the mountain lion in fifty years. "Already to me that's unacceptably high," says Riley. "If you have just a couple breeding males, and one month one gets hit by a car and one dies of rodenticide poisoning, then you're in serious trouble."

And that's before the detrimental effects of genetic inbreeding were considered. Once Riley and his team accounted for that, the risk of extinction by 2065 rocketed to 99.7 percent. It could even happen by 2030. Unless something can be done to help, mountain lions will all but disappear from Los Angeles, one of just two megacities in the world that's home to large cats. (The other is Mumbai, which boasts a healthy population of urban leopards.) 

But there's good news too. All they need to retain sufficient genetic diversity is at least one new lion joining the group every two to four years. "It's not like we need a parade of mountain lions marching across the freeway," says Riley. "One every generation makes a big difference." If those new lions successfully mate and produce offspring, the risk of local extinction plummets to under three percent. 

In Florida, conservationists worked to introduce lions from Texas, but in Los Angeles, given how small the habitat is and how large lion territories typically are, it would be merely a stopgap measure. Such a plan would not help young males born in the Santa Monicas, like P-22, successfully emigrate in search of new opportunities, nor would it help any of the other wildlife also hemmed in by highways, like bobcats. A more permanent solution is needed.

For several years, the #SaveLACougars campaign has argued vigorously that a wildlife crossing could be built over the 101 freeway near Liberty Canyon. Such a bridge would connect the Santa Monica Mountains with other lion populations to the north. One such advocate is Beth Pratt, California Director of the National Wildlife Federation, who is eager to arm herself with this scientific data. "It puts validity and rigorous science around the need for this crossing," she adds, an argument that she and others have already been making based upon an intuitive understanding of these animals, for years.

Christy Brigham, Chief of Resource Management and Science at nearby Sequoia and Kings Canyon National Parks, claims a personal victory with this paper. "It was me wanting to be able to say in a meeting, 'without a bridge they will all go extinct'," she says, that provided early motivation and support when she held the same post at the Santa Monica Mountains National Recreation Area. 

The analysis provides the planned wildlife crossing with a clear, objective metric for success, she says. "It gives us a nuanced understanding of how many individuals we need to cross, over a given time frame, to have the impacts we want on the population. Without knowing that, how do you say whether or not it's successful?"

Still, most Angelenos go about their lives never seeing a mountain lion at all. The survival of wild predators doesn't appear to have much impact on our day-to-day lives. Many will wonder why ensuring a sustainable future for the cats matters at all. But Pratt says that a wildlife crossing is about more than just mountain lions. "This is about reconnecting an entire ecosystem," she says. 

Southern Californians are beginning to see the early signs of a changing climate. We're stuck in the fifth year of an ongoing drought. Wildfires are burning hotter, faster, and more frequently. Healthy, vibrant ecosystems are better able to cope with these threats than degraded ones devoid of their fauna. "If mountain lions go, what's next?" she asks. "When you start seeing an ecosystem collapse like that, it impacts our well-being." If we help the mountain lions, we just might wind up helping ourselves.