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Why a mountain lion crossing a California highway is a big deal

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Why did the mountain lion cross the road?

P-55, the young male mountain lion that crossed the 101 Freeway.
Video by NPS / Flickr

In what researchers called a “rare case,” a young male mountain lion has successfully crossed the 101 Freeway near Thousand Oaks, California. This is only the fourth documented successful crossing of the freeway since 2002, according to the National Park Service, and it’s key for the big cats roaming around LA to move around, hunt, and spread genetic diversity.

The mountain lion, called P-55, was recently captured and tagged by the NPS in the western end of the Santa Monica Mountains; a GPS allows researchers to follow his movements. The fearless big cat has also crossed Highway 23 and the 118 Freeway, making him a bit of an outlier. When mountain lions stumble across a highway, they usually turn around. This has caused populations of mountain lions in California to be cut off from one another.

The mountain lion P-55 was tagged in April by the National Park Service.
Photo: National Park Service

A fragmented landscape is dangerous for the big cats: the animals need large swaths of land for hunting and mingling with each other. Isolated groups resort to interbreeding — a male mountain lion called P-12 is known to have mated with with his daughter and granddaughter, for instance. That, in the long run, reduces genetic diversity, putting a species at risk of extinction. Also, young males who can’t roam freely sometimes get stuck in another male’s territory, leading to conflict and possibly death.

Highway 101 is like a wall to mountain lions trying to move between the Santa Monica Mountains and other natural areas to the north. P-55 was recorded crossing the highway some time between midnight and 2AM PT on July 30th, a day after he was caught on video next to a hot tub in a backyard in Newbury Park. P-55 is now roaming the Santa Susana Mountains, the NPS says. But other mountain lions aren’t often as lucky: 17 big cats have been killed since 2002 while trying to cross highways in the region.

To solve the problem, local organizations have talked about building a wildlife bridge across the 101, just west of Liberty Canyon Road in the City of Agoura Hills. The overpass would allow mountain lions to move freely between the Santa Monica Mountains and Simi Hills, and ultimately out to the Sierra Madre Mountains. A similar wildlife bridge is under construction over Interstate 90, east of Keechelus Lake in Washington state, to allow bears, deer, elk, and other animals to roam freely.

If the overpass isn’t built and landscape fragmentation isn’t addressed in some other way, the declining genetic diversity could cause mountain lions like P-55 to go extinct in the next 50 years, according to a study published last year.