Anthropogenic disturbance induces opposing population trends in spotted hyenas and African lions

Large carnivore populations are declining worldwide due to direct and indirect conflicts with humans. Protected areas are critical for conserving large carnivores, but increasing human-wildlife conflict, tourism, and human population growth near these sanctuaries may have negative effects on the carnivores within sanctuary borders. Our goals were to investigate how anthropogenic disturbance along the edge of the Masai Mara National Reserve, Kenya, influences the demography and space-use of two large carnivore species that engage in intense interspecific competition. Here we document, in one disturbed region of the Reserve, a rapid increase in the population size of one large predator, the spotted hyena (Crocuta crocuta), but a striking concurrent decline in numbers of another, the African lion (Panthera leo). Anthropogenic disturbances negatively affected lion populations, and decreasing lion numbers appear to have a positive effect on hyena populations, indicated here by an increase in juvenile survivorship. We also saw an increase in the number of livestock consumed by hyenas. Our results suggest human population growth and indirect effects of human activity along Reserve boundaries may be effecting a trophic cascade inside the Reserve itself. These results indicate both top-down and bottom-up processes are causing a shift in the carnivore community, and a major disruption of guild structure, inside the boundaries of one of the most spectacular protected areas in Africa.