Possums love leaves packed with protein, an insight that could aid New Zealand's pest-control efforts.

Researchers from the Australian National University have just reported their findings in the international journal PLOS ONE, following a collaborative, Government-funded study with Landcare Research.

Each year, the Department of Conservation spends millions of dollars on 1080 poison and ground operations to combat possums which, in some forests have eaten whole canopies of rata, totara, titoki, kowhai and kohekohe.

They compete with native birds for habitats and food, disturb nesting birds, eat their eggs and chicks, and may also have an impact on native land snails.


Dr Hannah Windley from the ANU Research School of Biology compared the nutritional quality of New Zealand foliage with the damage possums do to trees by over-eating.

"We can use this new information to predict the impact possums have on forests in New Zealand, and it may also help in targeting control programmes for managing this pest," she said.

"By identifying the forests, or tree species, that have high digestible protein concentrations, strategies can be put in place to protect those forests."

Dr Windley analysed the nutritional value of leaf samples taken from 275 trees at four times of the year.

"It is surprising that any relationship between nutrition and the feeding decisions of possums could be detected at all," she said.

"There are many reasons why herbivores may eat from some trees and not others, and the fact that we could predict these feeding choices at a large-scale using a single nutritional measure highlights the important role that available protein plays in regulating possum populations in New Zealand."