First results of feral cats (Felis catus) monitored with GPS collars in New Zealand

Abstract

The presence of feral cats (Felis catus) in the braided river valleys of New Zealand poses a threat to native species such as the critically endangered black stilt (Himantopus novaezelandiae). Trapping remains the most common method to control introduced predators, but trap placement criteria have not been fully informed by advances in the understanding of the spatial ecology of the pest species. We assessed the suitability of Global Positioning System (GPS) tags to study the spatial behaviour of feral cats in New Zealand braided rivers. We tagged and tracked five individual adults, one female and four males. Tracking periods varied from 3 to 18 days at a fix rate of one location every 15 min. This rate was considered an adequate trade-off between battery limitations and the opportunity to approximate the continuous displacement path of a cat for a representative number of days. Individual home range size estimates (100% Minimum Convex Polygon, MCP) varied from 178 to 2486 ha. For four of the six cats incremental analysis revealed that at least 460 locations are required to calculate a home range using MCP. Habitat selection analysis showed significant differences among individuals tending to select ‘Mature riverbed’ habitats. Trapping effort should be focused on this habitat. Movements and distances travelled revealed that cats move mainly between mid-afternoon (1500 hours) and early morning (0300 hours). This study showed that GPS telemetry provides a powerful method to study feral cat movements in open landscapes in New Zealand.