Modeling Impacts of Hunting on Control of an Insular Feral Cat Population

When introduced to exotic ecosystems, feral cats can inflict irrevers­ ible harm on native fauna. This is especially true in insular ecosystems because endemic vertebrate species often lack predator defenses. Feral cat control pro­ grams have been implemented on islands throughout the world with varied success. Effective and responsible management of pest populations requires knowledge of the impact of control actions. Here, we examine a feral cat control program created for the protection of the critically endangered Mariana crow on Rota Island in the Commonwealth of the Northern Mariana Islands. We apply a discrete form of the Schaefer model to a 29­month time series of removal data. We use a negative log likelihood framework to determine maximum likelihood parameter estimates and Akaike’s Information Criterion for small sample size (AICc) analysis to determine the best­fitting model. The model indicated that the removal program on Rota initially reduced cat abundance from an estimated 1,218 to 952 individuals within the first 18 months and then maintained the population near 1,000 individuals for the following 11 months. Given the cur­ rent level of available funds, we suggest that application of uniform island­wide hunting effort may not be the optimal strategy to maximize crow protection; rather, we suggest a multifaceted, targeted approach focused on areas of high crow activity.