Managing apparent competition between the feral pigs and native foxes of Santa Cruz Island

This paper presents a model of pest impacts in a multispecies framework. Strong detrimental relationships often form between pest populations and other biota, damaging ecosystem services and reducing social welfare. Under these circumstances, optimal pest management must account for the interactions between pests and other species. The bioeconomic model of competition developed in this manuscript is illustrated using the case of feral pigs (Sus scrofa) on Santa Cruz Island, California. The presence of the pigs, an introduced species, resulted in the near extirpation of the native island fox (Urocyon littoralis) before managers intervened and removed the pigs from the island. The application compares a policy of pig eradication with one of perpetual control, which is found to involve initially over-culling the pigs relative to the equilibrium level. To protect the foxes of Santa Cruz Island, the results suggest that pig eradication rather than pig control is the optimal strategy.