Survival and competing mortality risks of mountain lions in a major metropolitan area

Abstract

Understanding natural and human-caused mortality for top predators persisting in human-dominated landscapes is critical for conserving their populations. We estimated survival and cause-specific mortality rates and investigated factors influencing mortality risk of mountain lions by radio-tracking 58 individuals (33 males, 25 females) across the highly fragmented landscape in greater Los Angeles, California from 2002 to 2019. Mortality risk did not differ strongly between subadults (annual survival [ŝ] = 0.68, SE = 0.08) and adults (ŝ = 0.81, SE = 0.04). However, the different age-classes were subjected to mortality risks from different sources as subadults were more likely to be killed by conspecifics, whereas adults were more likely to die from human-caused mortality. Male subadults were frequently killed by territorial adult males in the isolated Santa Monica Mountains, mortality that may be exacerbated by substantial anthropogenic barriers to dispersal in this landscape. We also tracked kittens tagged at natal dens in the Santa Monica Mountains and estimated survival to independence to be 0.63 (SE = 0.13). Higher mortality from anthropogenic causes for adults, whose survival has the greatest influence on population growth and extinction probability for mountain lions, highlights the importance of mitigation strategies to reduce human-caused mortality. Our work provides novel information about patterns of survival and mortality of mountain lions from the most urbanized landscape occupied by large carnivores in North America.