Possum Control


Possum - Trichosurus vulpecula

Why fight the possums?

The high population of possums in New Zealand is a major problem.  Each night, collectively, these pests eat several tonnes of vegetation.

Not only is the amount that possums eat a problem, but also the way they do it.  They are selective eaters, targeting tastier trees first before moving to other ones.

After being browsed, a healthy tree will put out new shoots in order to survive.  This new growth is the possum's preferred food, so again the tree will be heavily browsed.  After 2 years of being subjected to possum browsing, the tree's old leaves fall and it dies.

Moreover, possums also eat most types of berries and young seedlings.  As a consequence, the forests are dying, because the undergrowth only consists of species which the pests find unpalatable, instead of regenerating trees.

The result is a collapse of plant diversity and a threat to the food sources of native birds.

Controlling the possums

Sef set bait on a tree

Maara Roa possum pest control.
A lure is sprayed on trees to attract possums to the bait station.
A - bait station tube.
B - bait pellets (cereal dyed green).
C - flour based lure.

Initial attempts by the Friends of Maara Roa volunteers to control possums using Timms Traps were unsuccessful, primarily because of where these traps were located.  The poison-bait programme undertaken since 2002 has been much more successful.

A group of about ten people keeps down the numbers of possums in Maara Roa by helping with the possum control programme.  This involves checking a set of bait stations once every four to six weeks and keeping them filled with possum control pellets.  The bait stations are special tubes installed on trees in the bush, and kept filled with green-dyed cereal pellets containing brodifacoum.

The bait stations are systematically set out over the reserve in a series of nine lines and our helpers generally have responsibility for one or two of these.  Some of the bait station lines go over quite rugged land, so helpers need to be reasonably fit and active.  They go out in pairs and it usually takes about two hours to complete the job.

The Wellington Regional Council supplies the bait (Brodifacoum), provides maps, and maintains the physical access to the bait stations.

Kohekohe fruit is loved by possums: the more fruit, the fewer possums.

Kokekoke fruit

The possum control programme has been going for some time now and indications are that numbers have dropped significantly.  From now on, the aim is to control re-infestation from possums moving in from outside the reserve.

With low possum numbers, the trees grow faster and produce more fruit and so the bush regenerates more quickly on its own accord.  The attraction of the possum control programme for the helpers, apart from helping the bush return to health, is that they see parts of Maara Roa that most others do not, and they get some good exercise in the process!

If you are interested in joining this group, complete the form on our "How to be Involved" page.

The Possum Control Team - One Man's Story

The Possum Control Team doesn't get much "press", but during 2012 year we decided that needed some attention.  So, photographer Cheng joined team member Tony, when he patrolled his bait lines one afternoon in May 2012.

We've combined Tony's story and Cheng's photos on a new page (also accessible from our Photo Gallery page), so view it here:
The Possum Control Team - One Man's Story

Many thanks to Fanny Berger and Claire Carbou.  This page was based on material written by them.  They were 2 French girls (ENSAT Agronomy students) who visited and worked on this project during 2007.
Read the article: Dominion Post, 1 Sept 2007: Digging into hard yakka on foreign soil.