The Role of Lethal Control in Managing the Effects of Apparent Competition on Endangered Prey Species

Apparent competition is the process by which one prey species may indirectly cause the decline in another species by sustaining a common predator. I argue apparent competition caused Sierra Nevada bighorn sheep (Ovis canadensis californiana) and Channel Island fox (Urocyon littoralis) population declines in the mid-1990s. In the Sierra Nevada, mountain lions (Puma concolor) are believed to have caused bighorns to abandon their winter ranges, thus indirectly contributing to population declines. In the Channel Islands, golden eagle (Aquila chrysaetos) predation is thought to have reduced 3 resident fox populations by over 95%. I argue, in both cases, native predators are the primary cause of the declines. Additionally, I argue these predators are primarily sustained by hyperabundant alternative prey species. In such cases direct management, to include lethal control of predators and hyperabundant alternative prey, may be necessary to restore these endangered bighorn and fox populations.