Mountain lions, bobcats and other wildlife would have less chance of becoming roadkill if the state adopts a plan to build a landscaped bridge over the 101 Freeway in Agoura Hills, supporters of the proposal said Wednesday.

State agencies, elected officials and wildlife advocates urged the state to provide the much-needed link in an area where rampant development and highways have fragmented once-continuous habitat. The 165-foot-wide, 200-foot-long overpass near Liberty Canyon Road would connect the Santa Monica Mountains on the south with the Simi Hills and Santa Susana Mountains.

Large carnivores in particular have found the 101 to be a formidable barrier. Since National Park Service biologists began researching mountain lions in the Santa Monica Mountains in 2002, motorists have struck and killed a dozen of the big cats in the study area, including a male puma hit on the 101 near Liberty Canyon two years ago.

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Urbanization has taken a toll on Southern California’s mountain lion population, spurring battles over shrinking territory and a depletion of genetic diversity because of inbreeding.

Building the nation’s largest wildlife overpass would be ambitious, said Seth Riley, a wildlife ecologist with the Santa Monica Mountains National Recreation Area, a unit of the National Park Service. At the proposed site, the highway has 10 lanes of pavement, including exit lanes.

“I don’t know anywhere where people have tried to put such a large wildlife crossing over such a busy highway in such an urban landscape,” said Riley, who has led the mountain lion study.

Scientists long ago identified Liberty Canyon as the optimal location to build a wildlife passage because of the large swaths of protected public land on either side of the freeway.


On Wednesday, the Mountains Recreation and Conservation Authority released a long-awaited study by Caltrans concluding that a wildlife overpass was feasible. The projected cost would be $33 million to $38 million, according to the report. Proponents said they plan to seek most of the money from public coffers.

The Mountains Recreation and Conservation Authority is a local partnership among the Santa Monica Mountains Conservancy, the Conejo Recreation and Park District, and the Rancho Simi Recreation and Park District. The California Department of Transportation completed the project study with a $200,000 grant from the Santa Monica Mountains Conservancy.

Elected officials expressed enthusiastic support for the project.

“It’s critically important to provide a safe crossing over the busy 101 Freeway for wildlife,” state Sen. Fran Pavley (D-Agoura Hills), who lives near the proposed wildlife corridor, said in a statement. “Now we need local, regional and national financial backing.”


Pavley, who last year convened a group to help develop a state-of-the-art plan, added that the pathway would also help protect motorists, who could be killed or injured in collisions with animals.

Other supporters include Assemblyman Richard Bloom (D-Santa Monica), U.S. Rep. Ted Lieu (D-Los Angeles), Los Angeles County Supervisor Sheila Kuehl and Ventura County Supervisor Linda Parks.

The report was the necessary first step toward a final design. Caltrans is expected soon to begin preparing the required environmental document, to be funded by a $1-million grant from the State Coastal Conservancy. The public would be asked to weigh in during this phase, which would run through 2017.

The National Wildlife Federation and the Santa Monica Mountains Fund have launched an initiative to raise funds for the engineering design and construction expenses.


The overpass would feature drought-tolerant vegetation placed so that it helps funnel wildlife across. Riley said hikers, mountain bikers and equestrians would also be able to use the structure.

Wildlife overpasses and underpasses are popular in Canada, Europe and Africa. Christmas Island National Park in Australia features an overpass for the island’s millions of red crabs, a vital species that devours leaf litter in rainforests and recycles the nutrients.

The state of Washington recently broke ground on Interstate 90 near Snoqualmie Pass for the state’s first freeway overpass for animals. The 150-foot-long structure is designed to provide passage for black bears, cougars, deer, elk and even squirrels, mice and lizards.

Similar structures have aided wildlife in the Flathead Indian Reservation in Montana, where 30 species have been documented making more than 20,000 trips across the bridges a year.


Twitter: @MarthaGroves

martha.groves@latimes.com

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