Abstract: Repatriation and reintroduction of carnivores are often promoted as an approach to restoring ecosystem functioning. The role of carnivores – regulating prey populations through consumptive and non-consumptive mechanisms – is thought to be key in this process by promoting top-down effects. However, species recovery is increasingly occurring in human-dominated landscapes that feature novel ecological communities and interactions. Thus, the functional role of carnivores may be very different and may not restore the original dynamics we seek. To test if carnivore feeding parameters were affected in human-dominated landscapes and if these changes can be related to the niche variation hypothesis, we studied seven populations of pumas (Puma concolor) across their distributional range in temperate latitudes of the Americas and across a gradient of human disturbance. We deployed GPS collars on pumas to determine the environmental variables within their home range and quantified the population niche width, proportional diet, dietary specialization and similarity of individuals via stable isotope analysis. We found a great variability of prey composition in puma diet across populations, although native ungulates were broadly consumed in most of the sites. Pumas exhibited high diet similarity within each location, which suggests that individuals steer to a population optimum and do not reveal niche variation. The isotopic niche width was similar between populations, but the specialization index decreased as a function of the human footprint, as large native ungulates were more important in the diet in less disturbed areas, while domestic and small wildlife increased their contribution to diet in areas with higher human footprint. We think that human presence may be affecting the puma diet by two mechanisms: modifying the prey offer and abundance; and as an ultimate predator, changing the foraging decisions of the puma and promoting a subordinate role in this carnivore. Our results suggest that the diet and, therefore functional role of pumas is strongly affected by human disturbance, with pumas possessing a broader diet and becoming a less specialized predator in human-dominated landscapes.
