Wildlife Damage Management, Internet Center for


Date of this Version

Spring 2009


Published in Human–Wildlife Conflicts 3(1):20–29, Spring 2009. Published and copyright by Jack H. Berryman Institute http://www.berrymaninstitute.org/journal/index.html


Brushtail possums (Trichosurus vulpecula) were introduced into New Zealand from Australia in the mid-1800s and became a major invasive pest. They damage native biodiversity by browsing and predation, and they are a disease risk to the livestock industry by acting as vectors of bovine tuberculosis (TB). Management of possums includes their eradication from some offshore islands and control by trapping, shooting, and poisoning on the mainland. Possums have been eradicated successfully from some islands and greatly reduced in abundance in other areas of high conservation value or where they are infected with TB. However, possums are still at very high densities in many areas. Conventional control methods (i.e., poisoning and trapping) are expensive and may sometimes be contentious, and unless the population is eradicated, these methods must be applied in perpetuity. Biological control, especially immunocontraception, is being investigated as a more humane and cost-effective alternative that might avoid the need for ongoing control. Researchers have investigated the delivery systems of biological control agents and possums’ responses to them. Possum zona pelucida and possum sperm vaccines have caused infertility in female possums, but the proportion of individuals sterilized varied. A possum-specific nematode is currently under investigation as a potential vector for biological control agents. However, there is concern, especially among Australians, whose possum populations are protected, about the safety of releasing a self-disseminating biocontrol system into the environment. Therefore, bait-delivered fertility control is likely to be used in the near future. A system that integrates various biological controls, including fertility control and improved conventional control methods, is likely to reduce the possum populations in New Zealand.