Hard boundaries influence African wild dogs' diet and prey selection

Human-mediated changes in habitat structure may disturb predator-prey relationships. We investigated the influence of perimeter fences on the diet of a reintroduced population of African wild dogs Lycaon pictus Temminck 1820 in a 316 km(2), fenced reserve in South Africa, by tracking radio-collared individuals during hunting periods to determine dietary composition from observed kills. Nutritional status of impala Aepyceros melampus and kudu Tragelaphus strepsiceros prey, as measured by the percentage of femur marrow fat, was significantly lower than that of unselectively culled individuals. This supports the hypothesis that wild dog predation is at least partially compensatory. Fence-impeded kills (those for which escape was deemed to be compromised by the fence) comprised 40.5% of kills (n = 316), and 54.1% of all edible biomass consumed. Compared with fence-unimpeded kills, fence-impeded kills comprised larger species (32.9 vs. 25.0 kg, W = 25667.0, P << 0.001), older age classes for one prey category (female kudu: Fisher's exact test, P = 0.02, n = 65) and animals in better condition for adult impala males (Mann-Whitney, W = 111.0, P = 0.012, n = 28). Fence-impeded kills also provided greater catch per unit hunting effort (27.3 vs. 12.2 kg km(-1); chi(2) = 7.89, P = 0.005), resulting in longer interkill intervals. Movement of the pack towards the fence at the start of each hunting period suggested a decision to exploit the advantage that fences conferred for capturing prey.Synthesis and applications. By enabling coursing predators to capture prey that would otherwise have escaped, fences may reduce the compensatory nature of predation, causing shifts in predator-prey dynamics that could influence the ability of small reserves to support such predators. The establishment of larger conservation areas to reduce perimeter-to-area ratios should be encouraged to limit the undesired effects of fences on predator-prey dynamics.