Ranging behaviour of forest-dwelling ship rats, rattus rattus, and effects of poisoning with brodifacoum

Abstract

We radio-tracked five male and four female rats for 6 nights in primary forest at Rotoehu. North Island. New Zealand. From trapping we estimated rat density at the study site to be 6.2 rats/ha. Radio-tracking revealed mean (± SE restricted polygon home ranges to be three times greater in males i 1.1 ± 0.29 ha) than females (0.3 ± 0.04 ha). Male ranges ov erlapped considerably, whereas those of females were largely exclusive. The ranges of males encompassed sev eral temale ranges. Four radio-collared rats were retrapped and administered a lethal dose of the anticoagulant poison brodifacoum. During the 3-5 nights after poisoning but before death, we detected no significant change in home range area or utilisation, arborealitv. or movements. Further research is required to determine if rats prey on other fauna while fatally intoxicated or cause secondary poisoning after being eaten by other predator species. © 1995 Crown.