How Did the Mountain Lion Cross the Road?

Breaking ground in L.A. on the world’s largest, and most ambitious, wild-animal crossing.

liberty canyon proposed wildlife crossing
National Wildlife Federation

For the wildlife of the Santa Monica Mountains, the freeways in Los Angeles pose a manifestly deadly threat. The groan of engines, the whine of brakes, the sight of so much steel and rubber hurtling by at unimaginable speeds—the survival instinct screams: Stay away.

And yet, year after year, the mountain lions of Los Angeles attempt the sprint across. Many die trying. In July 2019, a male cougar known as P-61 became the first big cat tagged with a GPS collar to successfully cross the 405 Freeway. That September, he tried again and was struck and killed by oncoming traffic in the Sepulveda Pass. Two more mountain lions perished last year on the roadbed of Highway 101. At least 23 mountain lions have been killed by cars in L.A. since studies began in 2002.

At over 150,000 acres, the Santa Monica Mountains National Recreation Area is five times the size of San Francisco. It is the world’s largest urban natural area. However, wild animals cannot roam freely within its limits like the bison in Yellowstone and the bears of Yosemite. It’s an acute problem that has long occupied Beth Pratt, regional executive director of the National Wildlife Federation’s California Regional Center. “The open space is monumental,” Pratt says, “but it’s not connected.”

Four freeways cut the preserve into pieces and cut members of the same species off from one another, eroding genetic diversity. For the mountain lions, these lethal barriers have led to inbreeding, deformity, sickness, disease, early death, and domains of too small a size to sustain a healthy population. In a wild gambit to find a mate, a cougar may risk its life by attempting to traverse 10 lanes of whizzing traffic. Absent a radical change in the mountain lions’ habitat, wildlife scientists predict that the big cats could be locally extinct by 2050.

This article appears in the Spring 2021 issue of Alta Journal.

Fortunately, a radical change is in the works. Later this year, construction is due to begin on the longest wildlife crossing on earth, a bridge spanning Highway 101 where it cuts through Liberty Canyon in northwest Los Angeles County. The estimated cost is $88 million, to be paid through state conservation funds and private donations. The project has engendered unusually impassioned support from the public.

Other species bear the brunt of L.A. highway traffic: amphibians, reptiles, and coyotes among them. But none have emerged as a living symbol of western independence and natural wonder—threatened by the same society that reveres it—the way the mountain lion has.

California is the only state that bars hunting mountain lions—a special protection won through a ballot measure in 1990 (and championed by Judge William Newsom, father of the state’s future governor). When the California Department of Transportation asked the public for comment on the proposed bridge in 2017, 8,800 responses rolled in, the bulk of them overwhelmingly positive.

Among the big-ticket donors to the bridge’s building fund were a couple from Kansas who had visited the city only once but were so taken with the plight of its wildlife that they kicked in $675,000. Leonardo DiCaprio’s foundation chipped in $300,000.

The most effective spokesperson for the fundraising campaign has charisma and rugged good looks but is not, in fact, a person at all. It is the big cat known as P-22, whom Pratt calls “the Brad Pitt of mountain lions.” P-22 first came to attention nine years ago when he materialized in Griffith Park. To make that journey, he must have braved the California mountain lion equivalent of free soloing El Capitan: crossing both the 405 and the 101 freeways. After his discovery, the cougar was tagged and tracked. His flamboyant exploits included sneaking into the L.A. Zoo and munching on an unsuspecting koala, but even then the city seemed to gain respect for his gumption.

The public yearning for the bridge may go far deeper than P-22’s marquee value. Addressing environmental catastrophes like climate change and biodiversity loss can feel abstract and unreal. “With the crossing, you build it and see results,” says Pratt. “There is something very tangible.”

proposed wildlife crossing at liberty canyon map


The Liberty Canyon wildlife bridge will be the biggest but not the first. There are overpasses for crabs on Christmas Island and underpasses for salamanders in Massachusetts. But even so, experts warn that more crossings need to be constructed, at a faster pace, to keep up with humans pushing deeper into the interface of wilderness and urbanism. And crossings are wildly successful at protecting species and reducing costs to people. A study in Banff, Canada, whose national park has more than 40 wildlife underpasses and overpasses, showed that along one two-mile stretch where a crossing had been installed, wildlife-vehicle crashes were reduced from an average of 12 a year to 2.5, decreasing crash-related costs by 90 percent—over $100,000.

Elevating the slice of native habitat in Liberty Canyon that intersects with the 101—the third-busiest interstate in California—is no small feat. “We are literally approaching the project from the outside in,” says Robert Rock, who serves as the lead architect for Living Habitats, the firm designing the span. The overpass will be 210 feet long and 165 feet wide, with soil and native plants extending in each direction. Landscapers will lay an acre of local vegetation on the surrounding hillsides so that they seamlessly flow into the crossing. Living green walls will dampen light and sound—which will help nocturnal animals manage headlight beams and the rumble of cars below. Drought-tolerant plants will stand up to exhaust and particulates.

“The ultimate goal is for the crossing to carry the mountain lion across the road,” says Rock, though lizards, snakes, and toads are also likely to use the bridge. More than 300,000 cars pass through the area each day. “It’s an incredibly large audience who is going to see this,” he says. “We do care what it looks like. The structure itself is by nature something that has to be different, feel different, uniquely Californian and uniquely ecological in its core ethos.”

Rock’s research team includes a mycologist to analyze how fungi might help the crossing maintain its local flora and a soil scientist who collects nearby dirt samples and mushrooms that are specific to the oaks and arroyo willows in the project’s vicinity. The team is also collecting seeds from the area for propagation. Plants and fungi raised in a special nursery will be established on the span so that cougars and other native animals (including insects) will be moving through comfortably familiar territory. “We are bringing genetic material across to create an ecological stitch,” says Rock. Birds will benefit from the new green space, too; research shows that they change their flight paths to preferentially fly over vegetation.

The crossing has already demonstrated the ability to increase human connections throughout the city. When Warren Dickson, a co-owner of 3rd Rock Hip Hop, an entertainment company in Watts, first met Pratt through efforts to bring greener jobs to his community, he was initially confused: Why did white people care so much about these mountain lions? As he learned more about P-22 and the dangers he faced, Dickson started to see parallels in his own community. City planners had deliberately sliced through L.A.’s poorest neighborhoods with freeways, displacing thousands of Black families, separating neighbors with uncrossable rivers of concrete.

Dickson had already started to work on green community projects in his neighborhood, but wildlife was something completely new. He started to feel empathy and sympathy for the famous mountain lion. “The fact that he had to face these obstacles just to make his journey, he’s trying to survive. We can all relate to that,” says Dickson. “He’s trying to make his travels, and there are all these obstacles. He feels cut off because of all the things that we built.”

p 22 mountain lion
Of all the wild animals that roam Los Angeles, none has captivated the city like Griffith Park’s resident mountain lion known as P-22.

Watching P-22’s determination reminded him of people he knows who have been cut off from opportunities. “You need to make a system to allow more to thrive, without having to risk all that this one risked to get there,” Dickson says. “So if we see the crossing become successful for these animals, what if we create a so-called crossing for this community that needs to thrive as well?”

It’s a connective tissue that runs deep in a pulsing city of cars and noise and heat—making bridges to let creatures reunite across valleys. Dickson has made it a goal, with Pratt’s help, to bring back the story of P-22 and let the lonely mountain lion be a social justice symbol for his community. “I don’t really separate the causes,” he says. “We’re all here existing on this land, and we’re all trying to thrive.”•

Katharine Gammon is a freelance science writer based in Santa Monica.
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