Foraging behaviour at carcasses in an Asian vulture assemblage: towards a good restaurant guide

Abstract

SummaryVulture populations are declining steeply worldwide. Vulture ‘restaurants’ or feeding stations are a tool for maintaining and monitoring numbers, but individual species may be disadvantaged by the effects of carcass distribution, carcass size and interspecific aggression. To test the degree to which restaurants give opportunities for each species to access the food provided, we studied behaviour and morphology in three Critically Endangered species of vulture in Cambodia: the gregariously breeding and feeding White-rumped Vulture Gyps bengalensis and Slender-billed Vulture G. tenuirostris, and the solitary Red-headed Vulture Sarcogyps calvus. We video-recorded attendance time, attendance order and dominance behaviour at different-sized carcasses. Interspecific aggression at carcasses was least frequently shown by the ‘small’ White-rumped Vulture. The relatively ‘large’ Slender-billed and ‘medium’ Red-headed Vultures showed aggression more regularly and at similar levels. However, the latter avoids conflict by waiting until Gyps vultures are no longer crowding at the carcass, although its arrival at carcasses was correlated with total number of vultures present. While more numerous than Red-headed, the two Gyps vultures are more dependent on large carcasses, which increases their vulnerability to further declines in wild large ungulate species. Body size, number of individuals, hunger levels and carcass size and availability all influence carcass attendance behaviour. An increase in the number and spatial distribution of restaurants as well as of carcass size range could boost numbers of all vulture species.