Possum poo gives clue to possum numbers
Media Release: Wednesday, 19 March 2003
Researchers have found a new way to assess possum numbers – through checking their individual calling cards, or in other words, possum poo.
Playing possum: Finding the remaining possums after control operations is difficult. Landcare Research has found a way to count them by using DNA from possum droppings.
At present, official estimates of survivors are based on the number of possums caught in leg-hold traps. However, this method is expensive and time-consuming, and results are biased where possums have become trap-shy or, for some reason, do not encounter traps.
In a project funded by the Animal Health Board, Landcare Research scientists have found a way to extract DNA from possum droppings. They can then use the unique genetic profiles obtained from possum droppings to identify individual possums and estimate numbers of possums that are not killed or caught. The method is the first step to an unbiased way to determine exact possum numbers.
“ Because in some instances there are possums that you cannot hunt or trap easily, it’s difficult to estimate how effective a control operation has been,” says the project manager, Graham Nugent.
“Possums produce more than 100 small droppings a day, so you have much more chance of finding possum poo than finding possums. And of course, possum poo doesn’t try to hide from you.
“Our research shows that you can extract DNA from droppings anywhere up to 27 days old, depending on how much rain there has been.”
Mr Nugent says this technique for counting elusive wild animals may prove to be cheapest when the animals are scarce. “That’s because only a few DNA samples are needed to ‘capture’ some of the possums at least twice when there are only a few animals. It is the proportion of recaptures that is used to estimate possum numbers.”
Landcare Research geneticist Dr Dianne Gleeson says although examining possum poo is hardly glamorous, the results have been very exciting.
“We did not expect to have any success. However, by peeling the ‘skin’ off the droppings with a scalpel, we could find small numbers of DNA cells that have been sloughed off the walls of the possum’s gut.
“With this approach, we gain enough information to obtain individual genetic profiles of possums that remain at large.”
Dr Gleeson says the cost of the technique compares well to field counting methods, and will decrease as procedures are further streamlined. She says researchers can immediately start to use the technique as a tool to estimate possum numbers.
However, and perhaps unfortunately for her, this success has sparked similar projects.
“We are now working with deer droppings, to see if they can yield clues to numbers in the wild. But there are plans to extend this to wild pig poo.
“Deer and possum poo is bearable, but pig poo is pushing the limits of what we can tolerate.”
For more information please contact:
Graham Nugent
Landcare Research
Lincoln
(03) 325 6700 x2256
NugentG@LandcareResearch.co.nz
Dianne Gleeson
Landcare Research
Auckland
(09) 815 4200 x7081
GleesonD@LandcareResearch.co.nz
Tom Fraser,
Media Communications Manager,
PO Box 40,
Lincoln. 7640.
Phone: 03 321 9719
Fax: 03 321 9998
Mobile: 027 277 6183
Email: FraserT@LandcareResearch.co.nz