Carcass Density, Size and Visibility Do Not Significantly Differ Between Areas With and Without Spotted-Hyaenas (Crocuta crocuta), With Implications for Threatened Vultures

Changes in predator guild composition can affect obligate scavengers through facilitation and competition dynamics. In Namibia, declines of spotted-hyaenas (Crocuta crocuta) may influence threatened vultures, either positively, via provisioning carcasses, or negatively, as dominant scavengers competing for carcasses. To examine potential mechanisms of influence of spotted-hyaenas on vultures, we compared carcass densities, carcass size (live weight estimated by species, age class and sex), and potential visibility of carcasses to vultures between sites with and without spotted-hyaenas across Namibia. We sampled thirteen private protected areas (PPAs), six with spotted-hyaenas present and seven where they were absent. Carcass densities were estimated for each PPA using line-transect sampling, recording a total of fifty-four carcasses. There were no significant differences in carcass density, carcass size or carcass distance to cover, as a proxy for visibility, between areas with and without spotted-hyaenas. These results do not indicate mechanisms of either strong facilitation or strong competition with vultures, suggesting that spotted-hyaena activity on these Namibian reserves is not detrimental to vultures, but equally may not result in increased carcass availability.