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

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. L'embroussaillement devient progressivement un probl & egrave;me pour la conservation de la biodiversit & eacute; dans les savanes africaines. Si cet envahissement par la v & eacute;g & eacute;tation ligneuse peut g & ecirc;ner les oiseaux charognards tels que les vautours, qui recherchent principalement par la vue, il peut profiter aux mammif & egrave;res charognards qui recherchent par l'odorat. Cette & eacute;tude visait & agrave; examiner la capacit & eacute; des mammif & egrave;res charognards nocturnes et des oiseaux charognards diurnes & agrave; localiser les carcasses & agrave; des endroits o & ugrave; les densit & eacute;s de v & eacute;g & eacute;tation sont croissantes. Nous avons plac & eacute; successivement 27 carcasses d'impalas (Aepyceros melampus) & agrave; cinq jours d'intervalle dans un camp de chasse cl & ocirc;tur & eacute; de 2 000 ha offrant une large gamme de densit & eacute;s de plantes ligneuses. Les arriv & eacute;es des charognards et les premiers repas ont & eacute;t & eacute; enregistr & eacute;s & agrave; l'aide de pi & egrave;ges photographiques. Les oiseaux charognards, principalement des vautours & agrave; dos blanc (Gyps africanus), se nourrissaient exclusivement de carcasses pendant la journ & eacute;e, et les mammif & egrave;res charognards, principalement des hy & egrave;nes brunes (Parahyena brunnea), se nourrissaient uniquement la nuit. Les deux guildes se livraient donc & agrave; une concurrence d'exploitation sans interaction directe entre elles. Pour les vautours, le temps n & eacute;cessaire pour localiser une carcasse augmentait avec la densit & eacute; des plantes ligneuses. La densit & eacute; moyenne de plantes ligneuses & agrave; laquelle les oiseaux charognards localisaient les carcasses & eacute;tait de 2 188 plantes/ha, alors que les mammif & egrave;res charognards localisaient les carcasses & agrave; des densit & eacute;s sensiblement plus & eacute;lev & eacute;es de 5 156 plantes/ha. Les responsables de ressources doivent comprendre la synergie entre le maintien de la v & eacute;g & eacute;tation ligneuse au profit des mammif & egrave;res charognards nocturnes et le maintien des savanes ouvertes au profit des oiseaux charognards diurnes.