Mountain Lion Crosses 101 Freeway

Mountain lion known as P-64 has crossed the 101 freeway at future site for wildlife bridge.

23 National Park Service researchers have documented a rare case of a mountain lion crossing the 101 Freeway in the Liberty Canyon area of Agoura Hills, underscoring the area’s importance as the ideal location for a wildlife crossing.

An adult male mountain lion known as P-64 was captured on Boeing property at the Santa Susana Field Laboratory on February 28 and outfitted with a GPS collar. The following day, he headed south, and surprised researchers by crossing the 101 Freeway.

Trail cameras in the area show P-64, estimated to be three or four years of age, used a culvert that runs under the freeway to cross, and he is believed to be the same mountain lion that researchers have recently documented using that same culvert. His home range may include the northern portion of the Santa Monica Mountains, the Simi Hills, and the Santa Susana Mountains. Adult male mountain lions can have home ranges of up to 200 square miles.

“It’s really interesting that this mountain lion figured out how to use this extremely long and dark culvert under the freeway,” said Seth Riley, wildlife ecologist for Santa Monica Mountains National Recreation Area (SMMNRA). “We have had many other collared mountain lions come close to the freeway in the Liberty Canyon area and not manage to get across.”

National Park Service researchers have been intensely monitoring the area for nearly three years with several trail cameras, both along Liberty Canyon Road and in nearby natural areas. During that time, cameras have detected many different species including bobcats, coyotes, mountain lions, mule deer, and raccoons close to the freeway. However, biologists have not confirmed that any animals managed to cross to the other side of the freeway, until recently when it was discovered that P-64 used the culvert to cross.

From 1999-2000, CSU Northridge master’s student Sandy Ng monitored the same culvert with remote cameras and recorded zero bobcats, coyotes, deer, or mountain lions using it over a 12-month period. The culvert stretches more than 640 feet under the freeway, is sometimes full of water, and is completely dark because it bends along the way. The only animals detected during this earlier monitoring period were raccoons, skunks, and an opossum.

“This discovery is exciting because it reaffirms that the proposed wildlife crossing at Liberty Canyon is going in the right place and, once completed, will be used by mountain lions and other wildlife,” said Riley. “Though we clearly cannot count on the Liberty Creek culvert in general for connectivity, it shows the importance of this location and the ability and drive of these animals to find ways to get across,” said Riley.

Caltrans, along with numerous other partners, proposes building a wildlife crossing over the 101 Freeway and Agoura Rd. in the Liberty Canyon area and last fall released the draft initial study and environmental assessment for the project. A wide and vegetated crossing over the freeway would serve a broader range of species than a tunnel under the freeway.

The 101 Freeway is a major obstacle for wildlife movement between the Santa Monica Mountains and other natural areas to the north. That lack of connectivity has led to inbreeding and reduced genetic diversity among the mountain lion population in the Santa Monica Mountains. A study co-authored in 2016 with researchers at UCLA found that without increased connectivity, especially animals moving in from the north, this would lead to the continued erosion of genetic diversity and increase the chances of extinction of the mountain range’s population.

The lack of connectivity also limits dispersal of young male mountain lions, who at about one or one-and-a-half years old leave their mother to find a territory. Without the ability to easily leave the Santa Monica Mountains, young males become trapped in another male’s territory, potentially increasing the chances of conflict. While adult males generally overlap with many female lions within their territory, they will fight other males, which can lead to death.

Since the mountain lion study began in 2002, P-64 is only the fifth mountain lion documented to have crossed the 101 Freeway, and just the second, after P12 in 2009, to come into the Santa Monica Mountains from other natural areas to the north. During that same timeframe, 18 mountain lions have been struck and killed by vehicles on roads and freeways within the study area.

The purpose of the National Park Service research is to determine how mountain lions in and around the Santa Monica Mountains survive in an increasingly fragmented and urbanized environment.

The California Department of Fish and Wildlife is responsible for overseeing the management and conservation of mountain lions in the state.

Santa Monica Mountains National Recreation Area (SMMNRA) is the largest urban national park in the country, encompassing more than 150,000 acres of mountains and coastline in Ventura and Los Angeles counties. A unit of the National Park Service, it comprises a seamless network of local, state, and federal parks interwoven with private lands and communities. As one of only five Mediterranean ecosystems in the world, SMMNRA preserves the rich biological diversity of more than 450 animal species and 26 distinct plant communities. For more information, visit


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