The eradication of introduced Australian brushtail possums, Trichosurus vulpecula, from Kapiti Island, a New Zealand nature reserve

  • Published source details Cowan P.E. (1992) The eradication of introduced Australian brushtail possums, Trichosurus vulpecula, from Kapiti Island, a New Zealand nature reserve. Biological Conservation, 61, 217-226.


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.
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at:

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust