Hot or Hungry? A Tipping Point in the Effect of Prey Depletion on African Wild Dogs

Interspecific competition has strong effects within carnivore guilds, and African wild dogs are strongly limited by intraguild predation by lions and food loss to spotted hyenas. The densities of these dominant competitors correlate tightly with prey density, and prey depletion due to snaring is contributing to declines of apex carnivores across Africa. As a consequence of snaring, subordinate competitors like the African wild dog and cheetah are simultaneously experiencing a costly reduction in prey and a beneficial reduction of competitors. The net effect is difficult to predict. Here, we describe a previously unrecognized tipping point in the effect of prey density on wild dog density. Above this tipping point, wild dog density increases as prey density decreases, because the benefits of competitive release outweigh the costs of prey depletion. Below this tipping point, wild dog density decreases as prey density decreases, because the costs of prey depletion outweigh the benefits of competitive release. Conservation strategies for wild dogs must recognize this tipping point. As prey depletion due to snaring becomes severe, it limits wild dogs (mesocarnivores), just as it does lions and spotted hyenas (apex carnivores). Recent analyses based on time trends have argued that climate change is likely to cause wild dog populations to collapse. We suggest that prey depletion provides a mechanistically direct explanation of patterns in wild dog dynamics that have been attributed to climate change, and that the effects of prey depletion are likely to go unrecognized in the absence of data on trends in prey density.