Humans found to be leading cause of death for California’s mountain lions

Humans found to be leading cause of death for California’s mountain lions

Study looked at data from 23 areas of the state including the North Bay

The mountain lion world is abuzz with the recent publication of a scientific article highlighting the leading cause of death for these big cats in California: humans.   

The study, which was covered by UC Davis and Los Angeles Times, found that conflict with humans over livestock and collisions with vehicles were the primary causes of human-caused mortality in California mountain lions. Furthermore, livestock-related mortalities were linked primarily to “hobby” livestock holders with small numbers of animals rather than commercial livestock ranching. The study also found human-caused mortality to be more common than natural death, despite mountain lions being protected from hunting since 1990.

Non-fatal gunshot wounds can alter mountain lion behavior and increase depredation of pets and livestock

Quinton Martins, co-author and contributor to the study, leads the Living with Lions project in the North Bay. He looked at data from forty mountain lions tracked by the project since 2016; deaths were attributed to depredation (7), health (6), car strikes (3), infanticide (3), and abandoned den (2).

He has also documented non-fatal gunshot wounds in at least two of the collared mountain lions he’s tracking. “These injuries have likely impaired the lions’ ability to hunt their preferred wild prey, which could lead to an increase in depredation of pets and farm animals,” reports Martins. 

The case of the female mountain lion P1 is a prime example of displaying a dramatic shift toward livestock in her diet after being severely injured by gunshot. P1 was a 15–16-year-old female from the Sonoma Valley area who was killed after attacking a dog in someone’s house and killing livestock on the property. A necropsy conducted by the California Department of Fish and Wildlife (CDFW) showed that her elbow was completely shattered from a gunshot some time before, and she showed evidence of being shot on another occasion.  

A post-mortum x-ray of mountain lion P1 shows a shattered leg joint that may have led to diminished hunting ability

P33, a 3.5-year-old female whose home range includes Taylor Mountain Regional Park and parts of Trione-Annadel State Park, was limping badly from a gunshot wound when first captured and collared by the study. Fortunately, her gait appears normal again based on recent trail camera video footage and she is focusing on natural wild prey, suggesting the injury has healed well.  

A young female cat, P33, showed signs of a gunshot injury at time of capture, August 2022.

It is possible, but not confirmed, that P4, an 11-year-old female from the southern Mayacamas/Napa area, is a third case of a tracked lion being shot. When captured recently, she had facial trauma from a significant injury with a tear to her upper lip, cracked upper canine, and two shattered premolars. Confirmation of the cause of this injury that has significantly affected her feeding behavior will only come from a necropsy when she dies, however, a preliminary investigation suggests gunshot is possible.

Female mountain lion P4 has been tracked by the Living with Lions study since 2017 and reared several litters of kittens.

“P1 had killed livestock in the past, however, she was not a habitual livestock killer until the last year of her life when she focused almost exclusively on livestock. It is highly probable that this shift in diet for the last year was a result of the severe gunshot wound to the leg,” said Martins. “P4 has significantly increased her take of free-ranging pet cats and unprotected livestock since September 2022, most likely because of her injury which may have occurred then. She is still in good physical condition but taking longer than usual to consume prey,” he added.

A Puma Proof Pen design from Sonoma County Wildlife Rescue,

Predator-proof strategies are key to reducing mountain lion conflicts 

Sonoma County is home to around 75 mountain lions that traverse several hundred to more than ten thousand private parcels in each of their home territories. Black-tailed deer are the primary prey item for our local mountain lions, accounting for 70% of their diet, and pets and small farm animals account for about 20%; however, recent numbers have been skewed by the high level of pets and livestock taken by P1 and P4.  

“Killing mountain lions that attack unprotected livestock is not a viable solution for several reasons,” advises Martins. “It does not solve the underlying problem, and livestock may be attacked again when a new or another resident lion encounters them unprotected.” The primary way to keep pets and farm animals safe and reduce the risk of run-ins with both healthy and impaired lions is by adopting predator-proof strategies, including nighttime enclosures, guardian dogs for larger herds, and to a lesser extent, the use of sound and light techniques.  

We encourage anyone who cares for pets or farm animals to consider non-lethal ways to deal with wildlife conflict situations.     

Learn more about predator proofing from Sonoma County Wildlife Rescue

If you have a mountain lion conflict, contact Dr. Quinton Martins for advice on how to proceed: 707-721-6560 or [email protected]