The project’s particular focus has been on habitat use and movement, prey selection, health, human interaction, and connectivity among subpopulations that have been fragmented by urban development and highways. In 2016 and in collaboration with the Institute for Wildlife Studies, we expanded the research and geographical scope of the project to include mountain lions in the northeastern corner of California.
Further extension of our project occurred in 2022 when we added the Tehachapi Mountain Range north of Los Angeles, and the northern Gabilan and Diablo Ranges east of the Santa Cruz Mountains, to our portfolio of study sites. By placing global positioning system (GPS) collars on mountain lions, we are able to track lion movements and behavior and document habitat use. This information is critical for identifying potential conflict points in shared habitats, to help prevent tragedies for humans, pets, and wildlife, and to assist land and highway planners and conservation organizations to prioritize where their efforts should be focused. This information is also used to educate the public on the importance of mountain lions in the ecosystem and what can be done to prevent their decline in the state.
Since the main prey of mountain lions are deer, wherever deer are found across western North America, you are likely to find mountain lions as well. The human population is growing rapidly
Our studies show that mountain lions have large home ranges with an average of 125 square miles for adult males. Most at risk for human conflict are young males when they leave their mothers, because adult males will not tolerate young males in their territories. Many mountain lions have traveled tremendous distances in order to find new homes. In Southern California, that means crossing roads. Highways across southern California are major barriers and sources of mortality for this species, and are contributing in a substantial way to genetic restriction and the threat of local extinction for smaller isolated populations like those in the Santa Ana Mountains south of Los Angeles. Our research aims to increase understanding of current mountain lion connectivity across the major transportation corridors in the state that separate mountain lion subpopulations. GPS collar data can pinpoint focal locations where engineering interventions, such as new or improved wildlife crossings, can facilitate connections between populations. These crossings, when combined with appropriate fencing, can also reduce the incidence of lions killed by vehicle strike (roadkill), a key component to assuring long term population survival. Because of the increasing awareness of the negative effects of population fragmentation and isolation for mountain lions and other wildlife, we are using our current data, and will use data collected in the future, to advise Caltrans and others on the most effective highway crossing locations and designs.
In order to better understand mountain lion interactions with other species as prey, we regularly download data from GPS collars and investigate data clusters that may represent feeding sites. Mountain lions throughout their range prefer deer over any other prey species. They kill deer and return to kill sites over the course of several nights, covering the carcasses with leaves and grasses to preserve the meat and hide it from scavengers.
In areas where deer and bighorn sheep overlap in range, some mountain lions will take bighorn sheep for food. This is a concern especially in areas where bighorn sheep populations are struggling, and critical in areas where bighorn sheep subspecies are threatened or endangered. Thus, understanding factors that influence prey choice of mountain lions is critical for the conservation of other species too.
In the northeastern California study area, we are collaborating with the Institute for Wildlife Studies in their investigation of the ecological interactions between mountain lions and pronghorn antelopes, as these ungulates are of special interest for the California Department of Fish and Wildlife. In the northeastern study area elk and feral horses and donkeys are also food sources, and in the Gabilan and Diablo Range areas elk and wild pigs are alternative prey. In all our study areas, coyotes also make up a portion of the diet, as well as small numbers of domestic animals if they are present in mountain lion habitat and are unprotected at night from predators.
Health and disease
Wildlife health is linked to human and domestic animal health, which is why our team routinely assesses the health of mountain lions and bobcats that are captured. All animals are given a complete physical examination while under chemical immobilization, including blood, DNA and fecal sampling.
Our studies shows that mountain lions in southern California are exposed to a variety of infectious diseases, including Feline Leukemia Virus, originating in domestic cats (Petch et al. 2022). This is concerning in genetically restricted mountain lion populations, where proximity of mountain lions to domestic cats makes virus introduction possible, and where the outcomes of this could be fatal for the mountain lion.
Mountain lion exposure to anticoagulant rodenticides remains a concern in all of our study areas in California. The majority of the deceased southern California mountain lions that we have recovered and analyzed for these substances have tested positive for one or more of these compounds. In some mountain lions in our study area the levels were consistent with the amounts found in other mountain lions that have died as a consequence of the compounds’ direct toxic effects (Riley et al. 2007, Rudd et al. 2018). We have also begun detecting other rodenticides that can cause toxicity in mountain lions, such as bromethalin. This emphasizes that although rodents are not a primary prey item of mountain lions, that other animals such as coyotes that eat rodents are eaten by mountain lions and provide a pathway for rodenticides to impact mountain lions secondarily.
Human interaction, attitudes, and behavior
As the population of California grows and development expands into mountain lion habitat, conflicts are bound to occur. We continue to investigate methods of reducing conflicts between mountain lions, domestic animals, and people, especially in wild areas utilized by people, and rural areas where livestock are often kept in mountain lion habitat. This involves developing and testing deterrent devices and assessing mountain lion interaction patterns with humans and domestic animals in peri-urban or rural areas, and wildland parks.
Our team has worked to educate the public about how to avoid unnecessary risk when living in mountain lion country, and about the animals themselves and the issues they face. This educational work takes the form of presentations to the public and professional audiences, as well as a film series and full-length film about California mountain lions.
Avoiding back-country trails after twilight, hiking with companions, keeping children close, and protecting pets and livestock from potential attacks all enhance human safety in mountain lion habitat. Learning to see the world through the eyes of wildlife increases safety as well as increasing appreciation for our wild neighbors that help maintain healthy ecosystems for our benefit.