Feral pigs facilitate hyperpredation by golden eagles and indirectly causethe decline of the island fox

Introduced species can compete with, prey upon or transmit disease to nativ e forms, resulting in devastation of indigenous communities. A more subtle but equally severe effect of exotic species is as a supplemental food sourc e for predators that allows them to increase in abundance and then overexpl oit native prey species. Here we show that the introduction of feral pigs ( Sus scrofa) to the California Channel Islands has sustained an unnaturally large breeding population of golden eagles (Aquila chrysaetos), a native pr edator. The resulting increase in predation on the island fox (Urocyon litt oralis) has caused the near extirpation of three subspecies of this endemic carnivore. Foxes evolved on the islands over the past 20,000 years, pigs w ere introduced in the 1850s and golden eagles, historically, were only tran sient visitors. Although these three species have been sympatric for the pa st 150 years, this predator-prey interaction is a recent phenomenon, occurr ing within the last decade. We hypothesize that this interaction ultimately stems from human-induced perturbations to the island, mainland and surroun ding marine environments.