How many mountain lions live in California? New research offers an answer.

California researchers have long wondered: How many mountain lions live in the state? 

The last time researchers guessed at the state's mountain lion population was in the 1980s. Now, decades later, new research says there’s about 4,500 mountain lions in California. 

Justin Dellinger, a large carnivore biologist who led this latest research, announced the recent finding at a mountain lion working group meeting held at the California Department of Fish and Wildlife headquarters. A report on this research has not yet been published, but Dellinger plans to have it published in about a year. 

Dellinger said the old number — which estimated there were about 4,000 to 6,000 mountain lions in the state — was based on the amount of potential mountain lion habitat in California and an assumption on how many mountain lions would likely live in those areas. He described his recent finding as a more “scientifically rigorous estimate.” 

“The first one was just kind of a back-of-the-napkin approach,” he said. 

He said this estimate helps researchers understand the health of mountain lions overall. 

“Ideally, this serves as a baseline and, say, every 5 to 10 years, you update it so that you can look at things like the trend in the population,” he said. “Is it stable? Is it increasing? Decreasing?” 

He said one area of concern for researchers is mountain lions in Southern California. Roads and other human structures have limited their ability to roam, leading to more cases of inbreeding. This often causes reproductive issues, which could eventually lead to a decline in their numbers. 

But Dellinger said his research suggests there hasn’t been a steep population decline in the area just yet.  

“We still need to actively be working to restore connectivity in Southern California right now,” he said. “But densities and survival rate and things like that are showing us that they do have some time.” 

Dellinger said researchers like himself have long gotten questions about California’s mountain lion population from the public, especially because the last estimate was from decades ago. Finding the answer has been tricky; Dellinger said it took a lot of time and money to identify an estimate. 

Newer technology allows his team to both analyze mountain lion scat collected from their home range and follow their movements with tracking collars has helped.

“They didn’t have genetic capabilities [and] collars were pretty much in their infancy in that time,” Dellinger said of the limitations behind the decades-old estimate. “The technology is a lot different now.”   

But even with that technology at hand, he said mountain lions are fairly secretive and have large home ranges, making them a hard species to follow. 

“For some of us it might be our 10 to 20 square block area that involves our house, the gas station, the grocery store and friends… and that's a small area,” he said. “But mountain lions, it's just orders of magnitude bigger than what the scale at which people live their life.”

Winston Vickers, a wildlife research veterinarian with the UC Davis Wildlife Health Center, said Dellinger’s work sets the groundwork for future action to conserve mountain lions in California. 

“[Knowing] movement patterns can add protections in that they can guide highway agencies when they’re trying to most effectively deploy their resources to reduce wildlife impacts,” Vickers said. 

A recent UC Davis report noted an increase in mountain lion deaths on roads, meaning another threat to the species. Vickers said protections for mountain lions could include “new structures across highways or fencing to prevent roadkill.” 

Vickers added that it’s important people are aware of the impact human traffic and other activity has on mountain lions in order to solve this issue. He said losing a top predator would have a huge impact on the ecosystems mountain lions are part of. 

“We’re responsible for the majority of the mortality of mountain lions in California, either with our cars or responding to killing of livestock,” he said. “It’s all our responsibility — humans can prevent it all, if we choose to do so, or the vast majority.”