Eradications of invasive species from over 1000 small islands around the world have created conservation arks, but to truly address the threat of invasive species to islands, eradications must be scaled by orders of magnitude. New Zealand has eradicated invasive predators from 10% of its offshore island area and now proposes a vision to eliminate them from the entire country. We review current knowledge of invasive predator ecology and control technologies in New Zealand and the biological research, technological advances, social capacity and enabling policy required. We discuss the economic costs and benefits and conclude with a 50-year strategy for a predator-free New Zealand that is shown to be ecologically obtainable, socially desirable, and economically viable. The proposal includes invasive predator eradication from the two largest offshore islands, mammal-free mainland peninsulas, very large ecosanctuaries, plus thousands of small projects that will together merge eradication and control concepts on landscape scales.
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 iemale ranges. Four radio-coliared 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.
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