Thursday, November 26, 2009

How many possums are there in New Zealand?

Hello again,

I have spent the last two days at the National Possum Control Agencies (NPCA) (now the National Pest Control Agencies Oct 2011) Technical Transfer conference in Wellington. This conference is an opportunity to hear about best practice and new developments in the control of possums. It is focused primarily on the control of possums for the prevention of the spread of bovine tuberculosis in farmed and wild animals.

This year there were many interesting presentations but the one that has received the greatest interest from the media was the guestimate of the number of possums in New Zealand.

Bruce Warburton of Landcare Research has used information on the estimated possum densities that a wide range of habitats from farm pasture to native beech forest could sustain. He has then used satellite GIS information on habitat type to calculate the maximum number of possums NZ could sustain. This gave a value of 48 million. Information on possum control and monitoring, the areas under control and other information were then used to estimate the reduction in numbers in controlled areas. This reduced the number in NZ to 30 million suggesting the $80 million spent each year has reduced numbers by 36%.

Bruce was at pains to explain that there were many variables in his estimates that could influence the numbers greatly one way or the other so these figures should be viewed as guestimates only.

Bruce was subsequently interviewed by sections of the media who I note have already reported the numbers as if they are absolute. They have also taken the new 30 million estimate and compared it to the old estimate of 70 million and suggested the numbers have been reduced by 40 million!

What is the old saying? .........lies, damned lies and statistics.

No one knows how many possums there are. Bruce has made a good stab at estimation and the number is probably not far away. What is important is that the benefits of possum control in those areas where they are controlled far outweigh the costs.

Kiwicare manufactures and distributes one of the tools for the control of possums in NZ. The NO Possums Cholecalciferol Gel Bait that can be purchased from all good farm stores, hardware and garden centres is one of the newer tools in preventing possums destroying the New Zealand environment, causing economic loss and eating your roses.

A possum goes into the Shakespeare Bar in Stratford. To get the barman's attention he clears his throat.
The barman turns and asks "Tb or not Tb?"

1 comment:

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