Mountain Lion & Bobcat Project


The Karen C. Drayer Wildlife Health Center has worked with mountain lions in Southern California since 2001, with particular focus on:

We have placed GPS collars (and one VHS) on 65 lions to date. The collars allow us to track the movements and behavior and document habitat use. They also help us determine potential trapping sites. Using cage traps with road-killed deer for bait, we sedate the cats, take blood, DNA and feces samples to determine health, while also checking or applying collars.

The project has had great success using cage traps — a process far safer than snares or dogs, which continue to be the more prevalent capture methods.

Habitat Fragmentation

Since the main prey of mountain lions are deer, wherever deer are found across western North America, you’re likely to find lions as well. The population is growing rapidly in areas like Southern California, where habitat is becoming increasingly fragmented.

Our studies show that lions will range as far as 200 miles. Most at risk are young males when they leave their mothers, because adult males will not tolerate young males in their territories. Many lions have traveled tremendous distances in order to find new homes. In Southern California, that means crossing freeways.

Prey Animals

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.

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 are struggling, and critical in areas where bighorn sheep subspecies are threatened or endangered. More work is required to better understand mountain lion prey preferences.

We regularly download data from GPS collars and investigate data clusters that may represent feeding sites. So far, we have documented numerous instances of feeding on both bighorns and deer, as well as on smaller animals.

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 an examination including blood, DNA and fecal sampling. This research has lead to an increased concern about the levels of rodenticides and other toxins in captured felines.

A National Science Foundation-funded study is also tracking how viruses move between mountain lions, bobcats and domestic cats. Studying disease transmission not only gives us a better understanding of risk, but it also gives us surrogate information about how these animals move across the landscape.

Disease exposure data from our study shows that cougars in southern California are exposed to a variety of infectious diseases, some at relatively high prevalence. 

Cougar exposure to anticoagulant rodenticides remains a concern in our study area, as well as elsewhere in California. We have had samples from 23 southern California cougars analyzed for these substances and 100% of samples contained 1 or more of these compounds. In some cougars in our study area the levels were consistent with the amounts found in other cougars that have died as a consequence of the compounds’ direct toxic effects (Riley et al. 2007). The impact on cougar health of sublethal concentrations of these compounds is not well understood, but is of continuing concern and a subject of ongoing study into how these compounds are moving in the food chain.

Our data in combination with data from other cougar study areas suggests that levels of rodenticides may be highest in those individuals that circulate closest to human habitations (Riley et al. 2010), however, more samples from GPS-collared cougars with known circulation patterns are needed to strengthen this statistical analysis. Our collaborative research can help provide important understanding of the unintended impacts of these substances.

TrailsHuman Interaction, Attitudes and Behavior

As the population of California grows and development expands into mountain lion habitat, conflicts are bound to occur. Detailed knowledge of potential conflict points is essential to avoiding tragedies for humans, pets and wildlife. Our team has worked to educate the public about how to avoid unnecessary risk when living in mountain lion country.

Avoiding backcountry trails after twilight, protecting pets and livestock from potential attacks and learning to see the world through the eyes of wildlife are some basic safety tips.