Kapiti Island is a 1,965 ha nature reserve lying off southwest North Island, New Zealand. It supports the last (introduced) viable population of little spotted kiwi Apteryx oweni, and important populations of other native flora and fauna. Introduced to Kapiti in 1893, browsing activities of Australian brushtail possums Trichosurus vulpecula posed a serious threat to vegetation and associated wildlife. Possum numbers were reduced by sporadic trapping during 1920–1968. In 1980, an intensive programme aimed at possum eradication was implemented.
Due to the scale and complexity of the task, several Government management and research agencies with experience in possum control were involved. The island was divided into blocks; within each a network of mapped tracks was established to allow good coverage. A combination of trapping and hunting with trained dogs was used to eradicate possums systematically from each block. Aerial baited poison drops were also made from a helicopter, to cover about 330 ha of otherwise inaccessible, vegetated steep cliffs.
By the end of 1986 (i.e. 7 years after project initiation) possum eradication on Kapiti was achieved. Over the seven years about 21,000 possums were killed in about 1,399,000 trap nights, 4,500 hours of hunting with dogs, and aerial poisoning of cliffs.
Monitoring is being undertaken to assess responses of selected flora and fauna.
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