Mountain lions (also known as cougar, panther, and puma) are an important part of many natural habitats here in California. These elusive mammals can be found in any ecosystem that provides enough resources for them and for their prey to survive and thrive (One Health Institute, 2020). Cougars are considered as a keystone species and an apex predator; they have a great influence on the overall health of the ecosystem where they are located. For example, mountain lions help regulate deer and other mammal populations, helping to ensure that these animals do not become overpopulated. Uncontrolled population of these animals can negatively change the ecosystem by decreasing its biodiversity (Gilbert et al., 2017). Mountain lion populations are not doing well in Orange County due three major threats: (1) genetic isolation due to habitat loss and fragmentation; (2) cougar-vehicle collisions; and (3) depredation permits (One Health Institute, 2020).
Major Threats to Mountain Lions in California
Habitat loss and fragmentation threaten genetic diversity:
Habitat loss and fragmentation due to rapid urban development has led to the increasing lack of genetic diversity within mountain lion populations. Research on the cougar population in the Eastern Peninsular Range and the Santa Ana Mountains shows that freeways (e.g., Interstate 15 or I-15) and human development have greatly isolated one population from the other (Gustafson et al, 2018). This is an important issue because mountain lions need a large home range of 113 km2 to 485 km2 for migration and dispersal—with males needing a larger home range than females (Chartier-Grable, 1997). It is crucial for young mountain lions to find a home range that is far enough from those to whom they are closely related (e.g., mother, father, and siblings) to prevent inbreeding.
Signs of inbreeding include physical deformities, such as a kinked tail—which has been observed in the cougar population in the Santa Ana Mountains (Ernest et al., 2014). Inbreeding is a huge concern, especially for a smaller population, because it makes the population more vulnerable to diseases—which can ultimately lead to the species’ extirpation if there is low genetic diversity within the population.
In the Santa Ana Mountains, cougars looking for a home range sometimes need to cross the 8-10 lane I-15 freeway to reach the Eastern Peninsular Range (Gustafson et al., 2018). Mountain lions try to cross major highways “to maintain their large territory, or to discover a new home” (One Health Institute, 2020). Dispersal and migration of young mountain lions are crucial in ensuring that they don’t end up mating with their parents or siblings. Dispersal by crossing a major highway is a dangerous endeavor for mountain lions due to the high risk of them getting hit by a car. Vehicle collision, along with habitat loss and fragmentation and depredation permits, is a leading cause of mortality among mountain lions (Ernest et al., 2014).
Mountain lions are opportunistic hunters; they prey on unprotected livestock and/or domestic pets. California Department of Fish and Wildlife (CDFW) has been issuing depredation permits since 1973 (J. Dellinger, personal communication, March 16, 2021). If a mountain lion kills livestock or a domestic pet, the owner can request a depredation permit from CDFW that allows them to kill the mountain lion. According to Dr. Dellinger of CDFW, they are currently developing their depredation policy. Since 2019, CDFW has been implementing non-lethal measures when releasing depredation permits.
Several organizations, such as Caltrans, The Nature Conservancy, UC Davis Wildlife Health Center, and the engineering department of Cal Poly Pomona, are currently working on building a new crossing or improving existing habitat corridors so that mountain lions, and other migrating animals, can safely cross over I-15 (One Health Institute, 2019). According to Dr. Winston Vickers of UC Davis Wildlife Health Center, Caltrans and The Nature Conservancy are helping with creating a new habitat corridor along I-15 south of Temecula and upgrading Temecula Creek Bridge, which is an existing natural habitat corridor that connects the cougar population between the Santa Ana Mountains and the Eastern Peninsular Range (Raine, 2019). UC Davis is collaborating with faculty and students from the engineering department of Cal Poly Pomona to design new habitat corridors along I-15. There is also a plan to build a vegetative habitat corridor across the 101 freeway to help the cougar population in the Santa Monica Mountains. This proposed wildlife corridor would span the 101 freeway and Agoura Road in Agoura Hills, California.
Researchers estimate that the cougar population in the Santa Ana Mountains and Santa Monica Mountains may be extirpated in the next 50 years due to the decline in genetic diversity within each population (Kerlin, 2019). Therefore, the construction of these habitat crossings is crucial to the conservation of the cougar population in these areas. Individuals living in mountain lion country can help by educating themselves about the plight of mountain lions, driving more safely, protecting their livestock and pets, and avoiding attracting animals that are preyed upon by cougars. As a community, our collective effort is vital to the conservation of mountain lions in Orange County.