Changes in feeding behavior and patch use by herbivores in response to the introduction of a new predator

Abstract

Top-order carnivores are naturally returning, or are being reintroduced, in a number of places where they have previously been extirpated. To explore how prey species adjust their antipredator behavior in response to these predators, we measured giving-up densities (GUDs) in experimental feeding patches and time spent vigilant for greater kudu (Tragelaphus strepsiceros), sable antelope (Hippotragus niger), and warthogs (Phacochoerus africanus) before and after an introduction of wild dogs (Lycaon pictus). Before the introduction, the only predators in the system were cheetahs (Acinonyx jubatus). After the release, none of the prey species changed their microhabitat preference, in that they all preferred open grasslands to mixed tree and bush-clumps and bush-clumps. However, kudu and sable fed more intensively (i.e., achieved lower GUDs) and had lower vigilance in open grasslands, while reducing their feeding effort (i.e., higher GUDs) and increasing their vigilance near denser vegetation. When the wild dogs denned in the study site, potentially increasing contact with the prey species, the time kudu spent vigilant and their GUDs increased significantly across all patches, and continued to increase over time. In contrast, sable and warthogs stopped feeding from the experimental patches altogether during this period. The change in feeding intensity and vigilance levels by kudu likely reflected an additive antipredator response to both cheetahs and wild dogs, whereas sable and warthogs only responded to the increased risk from the wild dogs. Our results indicate that the addition of wild dogs influenced the foraging-safety trade-off for the 3 prey species, but that the antipredator behaviors utilized by these species to mitigate predation risk varied within the newly established 2-predator system.