December 21, 2014

L.A. Mountain Lions Trapped by Freeways

 

Increased connectivity is critical for the long-term survival of mountain lions.

PHOTO COURTESY OF THE NPS

L.A. Mountain Lions Trapped by Freeways

Mountain Lion P28 seen on a remote camera after catching some prey. Lions from the Santa Monica Mountains are hemmed in by freeways, the Pacific Ocean and the Oxnard agricultural plain, making the lack of genetic diversity a serious threat to their long-term survival.

That mountain lions have managed to survive at all in the Santa Monica Mountains of California—in the vicinity of the megacity of Los Angeles—is a testament to the resilience of wildlife.

Researchers, however, studying these large carnivorous cats now show in the August 14 Cell Press journal, Current Biology, that the lions are also completely isolated, cut off from other populations by the freeway. According to the researchers’ analyses, only one young mountain lion successfully dispersed into the Santa Monica Mountains in a decade.

Due to their almost complete isolation, the Santa Monica mountain lions show dangerously low levels of genetic diversity, the study shows. The circumstances have also made the Los Angeles-area cats incredibly sensitive to individual behaviors. That single male that immigrated in 2009 and successfully mated substantially enhanced the genetic diversity of the entire population all on his own.

“Many of these phenomena, including very low genetic diversity and close inbreeding, have only been previously seen in Florida panthers, an endangered and completely isolated population of mountain lions,” says Seth Riley of the National Park Service (NPS). “In our case, the fact that lions in the Santa Monica Mountains are completely surrounded by roads and development likely lead[s] to behaviors that would be rare or nonexistent if normal population and social processes could occur.”

Among those behaviors, Riley and his colleagues found evidence of close inbreeding events between fathers and daughters and of intraspecific killing, even of offspring, siblings, and mates, all behaviors that the researchers suspect would be rare or nonexistent if sufficient movement between populations was possible.

While one male lion moved into the Santa Monica Mountains during the study period, to the researchers’ knowledge not a single young mountain lion has successfully dispersed out, when normally 75 percent of young lions—all of the males and half of the females—would likely disperse. Riley says the one possible exception that proves the rule is a single male “who dispersed likely from the Santa Monica Mountains out to Griffith Park, where he lives in a tiny dead-end home range.”

Increased connectivity is critical for the long-term survival of mountain lions and other wildlife in the region, Riley says.

Unfortunately, no one was thinking about that 60 years ago when the Los Angeles freeway was built.

As a result, Route 101 is a development corridor, with very little natural habitat on either side. Riley says the National Park Service, the California Department of Transportation, and other local agencies have been working for more than a decade to try to obtain the funds for a wildlife crossing, ideally an overpass, for carnivores.

On the bright side, that one successful male immigrant shows that it might not take many successful crossings to get wild populations in much better shape at the genetic level. Otherwise, the future is easy to predict, Riley says.

“If wildlife connectivity is not considered and planned for, or improved in places like Southern California where it has mostly been lost, large carnivores, which exist at very low densities and need to move great distances, will not persist.”

THE NEED FOR LIBERTY CANYON WILDLIFE TUNNEL

Preliminary DNA results from the mountain lion killed last month on the 101 Freeway in Agoura Hills indicate the lion was traveling from the north and was on the verge of bringing new genetic material to the isolated population in the Santa Monica Mountains.

Wildlife advocates have long pushed for a wildlife tunnel crossing near the Liberty Canyon exit where this lion was struck and killed by a car.

Caltrans has twice come up short in applying for federal transportation funding for the $10M project. Another round of applications is expected early next year and the Santa Monica Mountains Conservancy is considering funding a study that would examine a variety of solutions to address the problem.

“The fact that this young male chose to cross—unsuccessfully—at Liberty Canyon shows how critical this wildlife corridor is for maintaining genetic diversity in the Santa Monica Mountains,” said Dr. Seth Riley, an expert on urban wildlife with Santa Monica Mountains National Recreation Area (SMMNRA), a unit of the National Park Service (NPS). “This section of the 101 Freeway is the ideal path into the Santa Monica Mountains because of the natural habitat on both sides of the freeway and the connections to large areas of open space.”

THE NEED FOR GENETIC DIVERSITY

Lions from the Santa Monica Mountains are hemmed in by freeways, the Pacific Ocean and the Oxnard agricultural plain, making the lack of genetic diversity a serious threat to their long-term survival. Working with the Robert Wayne Lab at UCLA and the Holly Ernest Lab at UC Davis, Riley and his colleagues have documented genetic differences in populations north and south of the 101 Freeway, as well as multiple cases of first-order inbreeding in which a father mates with his offspring.

Preliminary DNA results from three mountain lion kittens born in the Santa Monica Mountains in July indicate they are the result of inbreeding. The results underscore the need for improvements to the wildlife corridor that is currently obstructed by the 101 Freeway in Agoura Hills.

“Unfortunately, this litter of kittens is the latest example of first-order inbreeding in which a father mates with his offspring,” said Riley, an urban wildlife expert at Santa Monica Mountains National Recreation Area, a unit of the National Park Service. “Allowing safe passage from the Simi Hills into the Santa Monica Mountains is our best shot at addressing the lack of genetic diversity in the local population.”

The preliminary paternity results from UCLA’s Robert Wayne Lab indicate that Puma 12, known as P-12, is the father of the three new kittens, as well as the father of the mother, P-19.

The kittens, one male and two females, were born in the Malibu Springs area and were ear-tagged by biologists with the National Park Service last month. They are known as P-32, P-33 and P-34.

Though the new kittens appear to be healthy, inbreeding is just one of many challenges facing the mountain lion population in the Santa Monica Mountains.

NPS’s decade-long study to better understand how the animals survive in such an urbanized landscape shows that conflict with other lions, rodenticide poisoning and vehicle collisions are the top causes of death among more than 30 lions studied.

P-12 is the only radio-collared mountain lion documented to successfully cross the 101 Freeway, thereby contributing new genetic material to the isolated population in the Santa Monica Mountains. If this most recent lion had successfully crossed and mated, he would have brought new genetic material to the population south of the freeway.

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. 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.