Possums
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Possum.
Common name:
Possum
Scientific name:
Trichosurus vulpecula
Regional classification:
Service delivery, cost recovery and community control
Description
The possum, Trichosurus vulpecula, is an Australian marsupial which has spread throughout most of New Zealand since its first introduction in 1837.
Biology
In Northland, the average adult possum weighs 2-3 kg, and lives for about seven to nine years, Possums breed in autumn and often again around November. After a gestation period of 17-19 days the young possum is born hairless, blind, 15 mm long and weighing only 0.2 grams. It climbs into its mother’s pouch where it stays for five months before transferring to her back. Weaning occurs at six to eight months, and reproductive maturity is reached at two years of age.
Habits
Possums feed at night and sleep in nests or dens during the day. Nest sites can be inside walls or roofs of houses and sheds, in hollow logs, holes in banks, standing hollow trees, faults in trees, perching plants, clumps of flax, gorse, bracken fern, under tree roots or other dark dry places.
The heaviest concentration of possums is usually along the outer edges of bush or scrub, in horticultural areas or where there are good nesting sites situated close to a food supply. Possums are known to move one to two kilometres to feed but generally nest as close as they can to their food source and may travel as little as 50 metres a night.
They are reluctant to leave their dens in heavy rain, feeding only between showers and confining their movements to sheltered positions.
Although possums are tree dwellers, they can spend up to half the night on the ground and they can move across open land at a reasonable speed. They are very wary and appear to follow the same track night after night. This constant use produces a distinctive flattened pathway through grass or undergrowth, known as a possum pad. At times it is possible to follow this pad back to the nest site.
Why are they a problem?
Possums seriously damage native forests. They can destroy forest canopies and, in combination with deer or goats, eventually decimate tall forests. Rata, kamahi and tawa are especially vulnerable, as are Northland’s coastal pohutukawa forests.
Possums drastically reduce native birdlife by stripping forests of fruit, flowers and leaves which are vital food sources for birds. They eat the eggs and chicks of native birds, including the endangered kiwi, kukupa and kokako. They also prey on other forest wildlife - for example, they have caused the drastic decline of some native snail populations.
Possums damage horticultural crops, commercial forests and gardens.
In many parts of the country, possums carry the disease Bovine Tuberculosis. Northland possums are currently Tb-free. The presence of infected possums makes Tb control in cattle extremely difficult and costly, and poses a growing threat to our export beef, dairy and deer industries.
What can I do?
In order the preserve the best of our remaining native forests and wildlife, and to reduce the Tb risk for beef, dairy and deer export industries, it is vital reduce possum populations and keep them at low levels.
Recommended control methods
Poisons
There are three acute poisons - 1080, phosphorous and cyanide - which require a licence and are subject to strict control on their use. 1080 is not available for private use.
The four chronic poisons - pindone, talon, pestoff and campaign - require licences for their use and do not have the same restrictions as 1080, phosphorous and cyanide. However, they are generally more expensive and their effectiveness is dependent on many variables. It is important to follow the instructions supplied with them. You are welcome to contact your nearest Northland Regional Council office for advice.
All poisons pose risks to stock, humans and dogs as well as possums and the landholder must ensure that stock and dogs are kept away from poisoned areas.
Traps
Possum traps are set where appropriate, such as around farm houses. There are several types, the most popular being the Timms Trap, leg hold and box or cage traps.
Shooting
With the aid of a suitable spotlight, shooting can be effective in controlling possum numbers, especially when seasonal feed trees are targeted. However, frequent spotlighting will make possums gun-shy.
It is always best to use a variety or combination of methods for the best effect. Contact your local Northland Regional Council office for more information.
Find out more: Download possum control publications
More information
For further information or control advice please contact one of our Biosecurity Officers at the Northland Regional Council on 0800 002 004:
- Whangarei: Carl Cooper and Steve Henderson
- Dargaville: Paul Ralph
- Kaitaia: Mike Knight