The hidden lives of Sonoma Valley mountain lions

The future of mountain lions in Sonoma Valley and their extended ranges into Northern California hasn’t been written yet, but one of the possible futures can be found in Southern California where highways have had devastating effects.

While the mountain lion population in Sonoma Valley has remained relatively intact, the human development of highways and neighborhoods has fractured mountain lions’ habitat and caused a loss of genetic diversity in the apex predator.

“Southern California has got certain areas which are highly fragmented and and cut off these small pockets from the main source populations,” said Sonoma zoologist Quinton Martins. “They've got these really big issues there with 10 lane highways where animals are just simply unable to move between or cross.”

The result: A mountain lion population thread-bare on genetic diversity, cut off from other potential mates that could diversify the next generation’s gene pool.

There are a handful of adult mountain lions in Sonoma Valley, Martins said, and some have been the victims of car accidents and malnutrition in recent years. But the issue isn’t about a dwindling population, so much as connection to a main source population and the freedom to move, said Josh Rosenau, a conservation advocate at the Mountain Lion Foundation based in Sacramento.

“An adult female will have a home range of maybe 100 square kilometers, so 36 square miles, and will defend that against other females, at least,” Rosenau said. “And then male home ranges will often overlap those of about four females, so 200 to 300 square miles.”

But the belief that human development and conservation oppose each other is not necessarily true in the case of mountain lions. Development just needs foresight, said Caitlin Cornwall, a conservation planner at the Sonoma Ecology Center.

“It’s critical that the land not create lots of barriers to their movement, and those barriers are obvious things like fences, but also less obvious things like lights that are on at night,” Cornwall said. “A lot of ways in which what’s best for mountain lions is what is often called compact development or city-centered development. And it’s a lot of the same arguments as you hear for fire risks.”

Designs that take the animal’s well-being into consideration are critical, experts agree. Ronsenau said mountain lions are adept at hiding among humans — home videos often surface of someone just missing one of the big cats — but the real concern is that big cats have access to a suitable habitat where they can find enough deer and elk, and avoid living on top of one another, which can lead to infanticide by adult males. It also causes juvenile mountain lions to roam into areas they shouldn’t, like the one that was captured at the Santa Rosa Plaza shopping mall in 2019.

“Right now, things are still kind of functioning,” Martins said said. “You can still see this kind of movement and that. But the idea, I think, is to focus efforts on ensuring that it doesn't get worse, that the highways don't get bigger, that Highway 12 doesn’t become the next 405 or 101.”

Highways creating artificial sub-populations also has dramatic effects on the health of mountain lion genetics, causing in-breeding that leads to less health mountain lions overall, Rosenau said. Research into the mated pair that breeds Santa Monica’s sub-population have found kinks in the tails of mountain lions as a result of the in-breeding that’s taken place, according to National Park Service.

But as the need for infrastructure grows with the population in the North Bay, there will be more human development, which could imperil the habitats that mountain lions needs to survive and travel in search of territory. With the redevelopment of the Sonoma Developmental Center, the Sonoma Ecology Center has “dusted off” an old idea to aid the passage of wildlife from one area to the next.

“That idea is to raise a section of Highway 12... right where Oak Hill Farm is,” Cornwall said. “There’s two creeks there, Butler Creek and Hooker Creek, that cross under Highway 12.”

By raising this section of highway, it would create a passage beneath the road that would allow animals to cross without the risk of becoming roadkill, Cornwall said.

Mountain lions avoid areas that have human development or are too sparsely vegetated, Martins said, and have died as a result of crossing roads or starved in areas with little vegetation. On a satellite map, mountain lion habitat shows up as dark green spots of dense vegetation, Martins said, which makes it all the more important there are wildlife corridors that connect regions together.

“When you're looking at an area and you talk about corridors, mountain lions are really good ambassadors for border conservation. They're the species that highlight the integrity of an ecosystem,” Martins said. “They can they help direct us to where these corridors are.”

Based on tracking data of the mountain lions that live in Sonoma Valley, Martins has been able to see which routes the big cats use most, and how adolescent youth are traversing Northern California in search of a territory to call home.

There are two important corridors in Sonoma Valley. The one in Eldridge that is part of the Sonoma Developmental Center property and the other that extends north past Santa Rosa and connects to the largely unincorporated areas of Northern California.

“What you don't want to do is end up with a situation like the Santa Monicas where this Valley cuts off any movement over the Myacamus,” Martins said. “The SDC is an important location for movement of mountain lions within this area particularly.”

Mountain lions are the last remnant of California’s apex predators, which included the now extinct California Grizzly that adorns the state flag.

Contact Chase Hunter at chase.hunter@sonomanews.com and follow @Chase_HunterB on Twitter.