Spray doom to possums

By SIMON COLLINS

Scientists have developed a contraceptive for possums that could save New Zealand millions of dollars a year.

The contraceptive, in a spray, aimed at a female possum's eyes and nose, mixes a protein from her eggs into the cell wall of bacteria to trick her body into destroying her eggs as well as the bacteria.

Initial tests show that it cuts the possum's fertility by a third.

It could save a big chunk of the $78 million that the Animal Health Board spends each year on possum trapping, poisoning and research.

"This is the proof of concept we have been looking for," said Landcare Research scientist Dr Janine Duckworth.

"Our next aim is to further reduce fertility, by more than 50 per cent, and then to make the contraceptive effect last longer.

"If we can achieve this, the amount of poison used in New Zealand could be reduced by at least 50 per cent, and potentially more as we improve the vaccine."

The contraceptive is one line of inquiry in a suite of research projects aimed at blocking the possum's ability to breed.

Existing control methods using poison, traps and shooting have only temporary effects, as the population builds up again quickly as soon as the killing stops.

AgResearch said last month that it had found a tiny worm that sterilised the possums it infected.

Landcare was given a permit in 2001 to genetically modify carrots and potatoes to contain a protein, such as the new contraceptive, that would also sterilise possums.

Dr Duckworth said a bait would be easier to use than the present spray.

The institute plans to apply for a permit to conduct limited field trials of the contraceptive spray with wild possums in 2008.

Land Care Research