Home range, territorial behaviour and habitat use of stoats (Mustela erminea) in a colony of Hutton's shearwater (Puffinus huttoni), New Zealand

Abstract

We investigated home range size, territorial behaviour and habitat use of stoats in a colony of Hutton's shearwaters. A total of 15 stoats were caught, and radio-tracking data were obtained from 11 of them. Stoats tracked during the summer had very small home ranges (males 16.0 ha, females 9.4 ha), and with the exception of two immature animals, were defending intrasexual territories. Two males tracked in the spring had larger home ranges (47.9 ha) and were not territorial. Stoats showed a strong preference for areas where shearwaters were concentrated: 80% of tracking fixes were located in burrowed ground. The territorial behaviour of stoats is likely to limit the number of animals present within the colony during the shearwater's breeding season. Consequently, the small number of stoats within the colony (c. 20-30 adults) can kill only a very small proportion of the 100 000 pairs of Hutton's shearwaters present in the area. The low capture rate of stoats observed in this study indicates that capture rate is an inaccurate measure of stoat abundance when comparing areas of different prey availability.