A resource-efficient procedure to improve planning of invasive cat management on inhabited islets

Cats (Felis silvestris catus) are one of the most pernicious invasive species on islands, being responsible for the decline and extinction of many vertebrate taxa. Eradications programs are a powerful tool to fight against cat impacts on islands, but their implementation requires planning and design to prevent failure. In that sense, gathering data on cat habitat use, abundance and trophic interactions provides key information to effectively design management actions. The present contribution presents a simple resource-efficient methodology using cat feces to assess cat distribution, density and trophic ecology on an inhabited islet. This information is essential in order to effectively organize trapping efforts and minimize subsequent impacts of other species if a control or eradication campaign is undertaken. Additionally, our research effort evaluated the potential influence of coastal and anthropic resources on cat diet, which can also provide useful information for planning aside management actions. Cat distribution on our model islet, La Graciosa, was ‘clumped’, presenting higher densities in anthropic areas (villages and farms). The invasive house mouse and the European rabbit were the main prey items, although native invertebrates, reptiles and birds were also consumed. Cats on La Graciosa ingested a large quantity of garbage, which was negatively correlated with distance from human settlements. Considering the low time and resource requirements of this methodology, and the useful basic ecological information it provides, it can be employed to make optimal management planning decisions for small inhabited islands where cat control or eradication programs are being considered.