Finders' eaters: Increasing bush encroachment may shift carcass detection from diurnal avian to nocturnal mammalian scavengers

Abstract

Bush encroachment is increasingly becoming a problem for biodiversity conservation in African savannas. While this invasion by woody vegetation may hamper avian scavengers such as vultures, which primarily search by sight, it may benefit mammalian scavengers that search by smell. This study aimed to examine the ability of nocturnal mammalian and diurnal avian scavengers to locate carcasses at increasing vegetation densities. We successively placed 27 impala (Aepyceros melampus) carcasses five days apart in a 2000 ha fenced game camp that offered an extensive range of woody plant densities. Scavenger arrivals and first feedings were recorded with camera traps. The avian scavengers, mainly white-backed Vultures (Gyps africanus), fed exclusively on carcasses during the day, and mammalian scavengers, predominantly brown hyenas (Parahyena brunnea), fed solely at night. The two guilds thus competed exploitatively without direct interaction between them. For vultures, the time taken to locate a carcass increased with woody plant density. The mean density of woody plants that avian scavengers located carcasses at was 2188 plants/ha, whereas mammalian scavengers located carcasses at appreciably higher densities of 5156 plants/ha. Resource managers need to understand the synergy between maintaining woody vegetation to benefit nocturnal mammalian scavengers and maintaining open savannas to benefit diurnal avian scavengers.