RANGING BEHAVIOR OF FOREST-DWELLING SHIP RATS, RATTUS-RATTUS, AND EFFECTS OF POISONING WITH BRODIFACOUM

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 (1.1 +/- 0.29 ha) than females (0.3 +/- 0.04 ha). Male ranges overlapped considerably, whereas those of females were largely exclusive. The ranges of males encompassed several female 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, arboreality, 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.