Africa's apex predator, the lion, is limited by interference and exploitative competition with humans

Abstract

Apex predators are crucial for maintaining ecological patterns and processes, yet humans hinder their ability to fulfil this role by displacing them from the landscape. Many apex predator species such as African lions (Panthera leo) are experiencing catastrophic declines as a result of competition with growing human populations. Increasing our understanding of the competitive interactions between lions and humans, as well as identifying thresholds of lion tolerance to human activities are important both for lion conservation and our understanding of apex predator ecology in the Anthropocene. We investigated the relative and cumulative influences of anthropogenic pressures on lion occurrence across a 73 000 km2 multi-use landscape in southern Africa. We developed occupancy models from replicated detection/non-detection spoor surveys across gradients of anthropogenic and biotic features. We tested the two hypotheses that African lions were most limited by 1) interference competition with humans or 2) exploitative competition with humans and evaluated the relative contribution of individual anthropogenic and biotic variables to lion occurrence. Our models predicted that lions occupied 49% of the landscape. The strongest determinants of lion occupancy were negative associations with pastoralism and bushmeat poaching, and a positive association with preferred prey. Thus, lions in this landscape are limited by a combination of interference and exploitative competition with poachers and pastoralists. However, interference competition with pastoralism was the biggest driver limiting lion occupancy, with a clear disturbance threshold for lions cumulating in a near complete loss of lions from the landscape when cattle surpass 21% occurrence. This study provides a predictive understanding of the top-down impacts of humans on the world's vulnerable apex carnivores.