By Charlotte Tonkin
New research has calculated that there are around 30 million possums in New Zealand.
The number may seem high, but those in the pest control industry say the figure is an achievement.
And it's a far cry from inaccurate estimates in the 1980s which said there were as many as 70 million of the pests.
Possums threaten livestock, native wildlife and forests. Each year we spend $80 million trying to control their numbers.
Researcher Bruce Warburton is confident that the latest study shows accurate results.
“We were able to use a more sophisticated electronic system which they didn't have back in the 80s when the initial estimates were made” he says.
Using GPS systems to monitor where possums live and how many are in an area, Mr Warburton has calculated that without any control New Zealand could support a maximum of around 48 million. But as Mr Warburton explains, possum populations depend on the environments they live in.
“The big problem is trying to work out what the carrying capacity of the different forest types is, so some habitats might have 10 possums per hectare and other ones like exotic forests might only have two possums per hectare” he explains.
Possum control is carried out over half of all New Zealand’s land.
Various methods are used - in the main, trapping and poisoning.
The aerial use of 1080 only accounts for ten per cent of control efforts.
But success isn't measured by the number killed. It's based on the reduction of bovine tuberculosis and the increase of native flora and fauna.
Maurice Kennedy, the National Co-ordinator of the Pest Control Agency says signs are promising.
“In many cases there's contractors reporting the sounds of birds being deafening which is just tremendous” he says.
Possums were introduced from Tasmania in an effort to establish a fur trade. With no natural predators, their population exploded and Mr Warburton warns it's unlikely we'll ever be rid of them.
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