Los Angeles is the second largest metropolitan area in the US, but it's retained some of its natural wild side. In the mountains surrounding the metropolis, mountain lions — the last large carnivore in southern California — live, hunt, and try to repopulate. A team made up of scientists from UCLA and the National Park Service recently set out to see exactly how they're doing that hunting, given the increased encroachment of humans.

The researchers looked at pieces of land in the Santa Monica Mountains and Santa Susana Mountains, bounded on every side by freeways, farms, and urban or suburban communities.

They found that male mountain lions tended to choose wooded areas near water for their hunting grounds, and generally avoided human development. Researchers tracked over 400 kills and found that only two took place in developed areas. Females, on the other hand, surprised researchers by hunting much farther from these wooded areas and closer to development.

The UCLA / NPS team used GPS to find sites where mountain lions fed on mule deer.

The researchers' best guess as to why females would be willing to hunt so near to people — on average, a little less than a mile away — was that they were trying to avoid aggressive males. Female mountain lions travel with their kittens, and would want to avoid having them hurt or killed by their very close relatives.

Previous research suggested that the mountain lion's main prey, the mule deer, had been moving into developed areas during the last few years as a result of severe drought. Human-maintained water sources such as swimming pools, decorative ponds, and accompanying vegetation have lured the deer further into civilization, which has helped their own numbers grow. As urbanization has helped its prey, female mountain lions appear to have relocated closer to people as a result.

mountain lions are trying to find a balance with humans

For the most part, "mountain lions in and around LA appear to be doing a good job of finding places to hunt for deer while generally staying out of the way of humans," John Benson, a wildlife biologist at UCLA and one of the authors of the study, told The Verge. At the moment, this relationship is delicately balanced, and the mountain lion population is stable.

However, Colleen St. Clair, a biologist who worked on a similar study at the University of Alberta (but who did not contribute to this study), noted that the findings should serve as a cautionary message: "[The study] suggests that mountain lions are trying to find a balance between using the resources that occur near people without actually encountering them... but we're going to have to find new ways to manage conflict. In other words, don't combine attractants for deer and hiding cover for mountain lions near places where humans live and recreate!"

While they are also plentiful in most of the western United States, mountain lions face unique habitat challenges in the greater Los Angeles area. They aren't considered an endangered species in California, but they are large carnivores that need uninterrupted swathes of land for hunting and for roaming between groups to spread genetic diversity and repopulate.

(National Park Service)

Right now, groups of mountain lions are cut off from each other by highways — they have the lowest genetic diversity of any animal besides the Florida panther, which nearly went extinct. Jeff Sikich, a biologist with the National Park Service and another of the study's authors, told The Verge that this is the greatest immediate threat to the mountain lion populations in California, noting that biologists have recorded male lions mating with their daughters, and even grand-daughters, further dwindling the genetic pool.

the greatest threat to mountain lions is a lack of genetic diversity

An oft-proposed solution to this problem is a wildlife bridge connecting two of the largest mountain lion habitats — it would run directly over 10 lanes of the 101 freeway. It would not be the first time such a measure was taken in the US, though it would certainly be the most ambitious effort. And while the idea may sound far-fetched, there is significant support for it. The National Wildlife Federation is raising funds to contribute to the estimated $30 to $38 million project, which was declared feasible by the California Department of Transportation last year.

Sikich expressed his enthusiasm for the project: "There's a lot of momentum, and the public seems to be behind it. Most people love knowing that there is a large carnivore that remains in the Santa Monica Mountains, and the mountain lion is the last one we have left."