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Environment

Possums

 

Possum (Trichosurus vulpecular) Photo: DoC.Possum (Trichosurus vulpecular) Photo: DoC.

 

The brushtail possum is a serious pest to native bush, exotic forests, pastoral farms, orchards, nurseries, parks and home gardens. It is one of the most costly nuisances ever introduced to New Zealand and there is now no prospect of completely eradicating it, but we can take steps to control them.

 

Possums eat native trees and plants, berries, flowers, insects and snails. Rata, kamahi, tawa and pohutukawa are especially vulnerable to possum damage as these tree species are more palatable. They are also known to eat the eggs and chicks of native birds including the endangered kiwi, kukupa and kokako.

 

Possum.An adult possum in Northland weighs 2-3kg and can live for about seven to nine years. They breed in autumn and often again in November. Possums are nocturnal, feeding at night and sleeping in nests or dens during the day.

 

They carry and spread Bovine Tuberculosis (Tb) however Northland possums are currently Tb-free. It is vital that possum populations in our region remain low to reduce the risk of Tb being spread in Northland. 

Controlling possums

The three options to control possums are:

  • Trapping 
  • Shooting
  • Poisoning

Traps

There are two main types of possum traps – live capture or kill traps. As with poisons, each has advantages and disadvantages depending on the situation.

 

Kill traps

There are many different designs but the principle is to quickly and humanely kill the possum. Some traps are better than others and often the way the trap is set can make a difference to its effectiveness. Timms traps – which are effective and easy to set – are one of the most common kill traps available.

 

The main advantage of kill traps is that they don't need to be checked daily. Traps may be left in place for long periods and they are cost-effective as a long-term control technique.

 

Kill traps are seen as a danger to domestic cats however any risk can be reduced by using baits which cats won't eat or by keeping them indoors while traps are set. Traps can also become weak or worn over time and not kill humanely.

 

Possums can also become trap shy if kill traps are not set correctly and they can be dangerous to other non-target species for the same reason.

 

Timms trap and Possum in Timms trap.The Timms trap - easy to use and one of the most common kill traps.

 

Live capture traps

There are two main types of live capture traps. The first is usually a box or cage which is baited to lure an animal in, then the door is activated to close and lock behind it. The second are leg-hold traps which are small steel spring-loaded jaws that clamp and hold the possum's leg just above the paw when it stands on the trap.

 

Box or cage traps usually work well around built areas where non-target species may be at risk. Trap-shy animals can also be lured in by pre-baiting around the outside of the trap with favoured bait.

 

Animals caught are unharmed but must be humanely disposed of. (It should be noted that the once common method of drowning has been found to be inhumane and is now illegal).

 

Leg-hold traps have a long history of being very effective at catching possums for both control and the fur trade. Leg hold traps with serrated jaws and large traps with unpadded jaws are now banned. Also as protection for cats, no leg-hold trap may be set within 150 metres of a dwelling without permission from the occupier.

 

For up to date changes to laws concerned with the use of leg-hold traps please check the animal welfare section on the Ministry of Agriculture and Forestry Biosecurity NZ website:

 

www.biosecurity.govt.nz

 

With any live capture trap there is a legal obligation to check it within 12 hours of daylight each day. New possum traps are in constant development including self-setting and multiple-kill traps. For any news on new traps contact the Northland Regional Council.

 

Shooting

Possum.Night shooting possums using a spotlight is a popular method of control in semi-open areas where access at night is easy.

 

The red eye reflections of a possum can be easily seen and by knowing the seasonal feeding habits and targeting these areas, possums can be controlled. However, possums can become light shy and avoid hunters.

 

Shooting can also become less effective if over-used particularly when possums are regularly missed.

 

A .22 calibre firearm is usually best for shooting possums when limited to areas where firearms can safely be used by a licensed person. 

Poisons

Poisoning is the most cost effective way of controlling possum populations.

 

The table (below) lists four registered poisons that private landowners can use to control possums. Two of these require a controlled substance licence (CSL) while the other two are available for use without a licence however they are subject to some restrictions.

 

CSL required

No licence required

Cyanide paste

Encapsulated pellets (Feratox®)

Cholecalciferol paste (Feracol®)

Phosphorus double-strength paste

Brodifacoum cereal pellets

(Talon® or PESTOFF®)

 

Each of the poisons has advantages and disadvantages depending on where they will be used and the degree of control you want. Council staff – or other pest control experts – can advise you about the best poison control for your situation.

 

Possum feeding in tree (Photo: DoC).Other toxins are currently in development and the council can also provide an up-to-date status on these.

 

You can get a CSL licence through an Environmental Risk Management Agency (ERMA) approved assessor. A list of local assessors is available through ERMA – go to: www.ermanz.govt.nz for more information – or the Northland Regional Council. 

 

Poison bait stations

Possum bait stations are a safe, effective way of dispensing poison baits to possums.

 

Bait stations come in a variety of shapes, sizes and prices. Key features to look for are how well it will weather, how easily filled and how easy possums can feed from it. A bait station protects the bait from the weather which increases the effective life of the poison. 

Trails

Possums will regularly use the same trail (often called "pads" or "runs"). Look for flattened grass through paddocks, or narrow trails off ridges through forest.

Trees

Bark may be worn smooth and claw marks can be seen on the bark or around the base of trees. Also look for bite marks on the base of trees.

Droppings

Droppings are small, rounded pellets about the size of jelly beans.

Foraging damage

Possums often bite the new buds off fruit trees and the new growth off roses. They leave jagged leaf stumps when they tear the leaves from plants.

 

Under the Northland Regional Pest Management Strategies (RPMS), possums are suppression animals, meaning they are widespread throughout the region. The aim is to reduce possum numbers so the impact on the community and environment is decreased.

 

Possum eating an egg (Copyright: Nga Manu Images).

 

Find the brochure: Download the possums publication

More information

For more possum control information contact Northland Regional Council Biosecurity staff on:

0800 002 004 or refer to the Regional Pest Management Strategies at:

 

www.nrc.govt.nz/pestmanagement

 

www.npca.org.nz or www.ermanz.govt.nz