The relative effects of prey availability, anthropogenic pressure and environmental variables on lion (Panthera leo) site use in Tanzania's Ruaha landscape during the dry season

African lion (Panthera leo) populations have been reduced by almost half in the past two decades, with national parks and game reserves maintaining vital source populations, particularly in East Africa. However, much of the habitats necessary to support lion populations occur in unprotected lands surrounding protected areas. There is an ongoing need for understanding the ecological determinants of lion occurrence in these unprotected habitats, where lions are most vulnerable to extinction. This study evaluated variations in lion site use along a gradient of anthropogenic pressure encompassing the Ruaha National Park, Pawaga-Idodi Wildlife Management Area (WMA) and unprotected village lands via camera-trapping. We collected lion occurrence data in the dry seasons of 2014 and 2015, and modelled lion site use as a function of environmental and anthropogenic variables under a Bayesian framework. We recorded 143 lion detections within the national park, 14 in the WMA and no detections in village lands. This result does not imply that lions never use the village lands, but rather that we did not detect them in our surveys during the dry season. Our findings suggest that lion site use was primarily associated with high seasonal wild prey biomass in protected areas. Thus, we infer that human-induced prey depletion and lion mortality are compromising lion site use of village lands. Seasonal prey movements, and a corresponding concentration inside the park during sampling, could also play an important role in lion site use. These findings reinforce the need to secure large-bodied prey base to conserve lions, and the importance of protected areas as key refugia for the species.