Highways, Inbreeding, and California’s Mountain Lions
- Wendy Kaplar
- Jun 9
- 2 min read
In February, California wildlife officials voted to extend threatened-species protections to roughly 1,400 mountain lions across the Santa Cruz Mountains, Central Coast, Santa Monica, San Gabriel, San Bernardino, Santa Ana, and Eastern Peninsular ranges.
This decision followed a 2019 petition, temporary protections that began in 2020, and a state review that the California Department of Fish and Wildlife completed in December 2025. In February 2026, the California Fish and Game Commission unanimously voted to list the Southern California and Central Coast mountain lion population as threatened under the California Endangered Species Act. CDFW said in February that the commission would adopt its formal findings at a future meeting.
Mountain lions have inhabited these areas long before highways crossed them. Today, roads kill mountain lions and isolate some populations.
In May, vehicles struck and killed two young mountain lions in the long-term National Park Service study area within two days. A 6-month-old male kitten died on Las Virgenes Road between Mulholland and Lost Hills Road. Two days later, a young female, thought to be just under a year old, was struck on Mulholland Drive east of the 405 Freeway. She was one of the few mountain lions the National Park Service has documented in the Hollywood Hills.
For small, isolated populations, deaths like these are not just individual losses. Each young lion that dies on a road is one less that might have reached new habitat, found an unrelated mate, and helped keep genetic diversity from shrinking further.
When mountain lions cannot move between ranges to find unrelated mates, inbreeding can occur. Researchers studying Southern California mountain lions have documented kinked tails, undescended testicles, and abnormal sperm, all signs that inbreeding may be affecting reproduction.
