Habitat use by three rat species (Rattus spp.) on Stewart Island/ Rakiura, New Zealand.

Abstract

(R. exulans), was measured in four vegetation types on Stewart Island/Rakiura, over six consecutive seasons. Ship rats were found in all four vegetation types and dominated in podocarp-broadleaf forest and riparian shrubland. Norway rats were most common in subalpine shrubland and Pacific rats dominated in manuka (Leptospermum scoparium) shrubland. Analysis of micro-habitat affinities for the three species showed that ship rats were habitat generalists. Norway rats were associated with plants of damp sites. Pacific rats showed a significant positive relationship with increasing amounts of the ground cover wire rush, (Empodisma minus). Reasons for the observed habitat use on Stewart Island could include physiological adaptation to cold and wet conditions in Norway rats; the avoidance of predation or inter-specific competition by Pacific rats; and possibly preference for more structurally complex vegetation types by ship rats. ____________________________________________________________________________________________________________________________________