POSSUMS (TRICHOSURUS-VULPECULA) ON HAWKES BAY FARMLAND - SPATIAL-DISTRIBUTION AND POPULATION-STRUCTURE BEFORE AND AFTER A CONTROL OPERATION

Over 6.5 years, 723 possums were live-trapped and marked in swamp, wil low, and farmland habitats on approx. 350 ha of two adjoining sheep fa rms in Hawke's Bay, New Zealand. About equal numbers of males and fema les were trapped in each habitat, but males were recaptured more often than females. Eighty-five percent of the possums were trapped along t he margins of swamp and willow habitats that comprised only 6% of the study area. The swamp habitat contained at least 8.8 possums ha(-1), t he willow habitat 16.7 possums ha(-1), and the farmland habitat 0.13 p ossums ha(-1). Possums generally moved less than 200 m between success ive recaptures, and there were few trap-revealed movements between hab itats. Possums on part of one farm comprising 23 ha of swamp and willo ws were then poisoned with cyanide in bait stations. Two hundred and f ifty-eight possums-including 142 previously marked animals-were found dead, an estimated 90% of the population. Fifty-nine percent of the ma rked possums were poisoned within 100 m of their most recent trapping point, and 85% within 200 m. Proportionately more adult possums were k illed on the first night's poisoning and more juveniles on subsequent nights. After the poisoning, the surviving possums showed very varied responses to the reduced population density, ranging from no change in location or range of movements to changes in location, range of movem ents, or both.