Home ranges of ship rats in a small New Zealand forest as revealed by trapping and tracking

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Abstract
The home ranges of 5 ship rats (Rattus r. rattus L.) in a small forest area near Palmerston North were determined for 7 months by concurrent cage-trapping and smoked paper tracking. Baited tracking platforms were over 20 times as effective as cage-trapping in obtaining location data, and home ranges revealed by tracking were on average 5 times the area of trap-revealed home ranges. All the rats were to some extent cage-trap shy. However, although cage-traps could not supply useful information on range boundaries or swift acknowledgment of boundary changes, centres of activity calculated from trap data were comparable with those from tracking data. Tracking rates of individuals were variable; it would be risky to assume that they accurately reflected intensity of use of any area over short periods or when rats may have been competing for baits. The rats had stable home ranges; 3 females had ranges predominantly exclusive to each other. The progressive removal of individuals from the study area effected the prompt expansion of adjacent ranges to include vacated areas; that is, range size was inversely related to rat density.