Urban possum control work needed - study

University of Otago zoology master’s graduate Charlotte Patterson is the lead researcher in New...
University of Otago zoology master’s graduate Charlotte Patterson is the lead researcher in New Zealand’s first rigorous estimates of possum density in urban areas. PHOTO: PETER MCINTOSH
Dunedin backyards are home to possums.

Researchers have not only confirmed possums live in the city, but now think there could be enough of the introduced marsupials in parts of the city to damage native trees, birds and insects.

University of Otago zoology master’s graduate Charlotte Patterson has published New Zealand’s first rigorous estimates of possum density in urban areas.

In collaboration with Manaaki Whenua-Landcare Research, she led a study that ear-tagged scores of possums in Dunedin.

It showed there were enough animals that ‘‘at least call parts of backyards their home’’ that control work was justified in both public areas and private properties, she said.

In the forested areas around Jubilee Park there were estimated to be more than three possums per hectare.

At that level the pests could be causing ‘‘dieback’’ among favoured tree species, Ms Patterson said.

Researchers tested three areas in the city: a ‘‘fragment’’ of urban forest at Jubilee Park, and two residential areas, in Wakari and Maori Hill, each representative of different types of urban possum habitat.

The researchers used about 70 live-capture traps over eight days in each area.

Camera traps were used in the two residential areas to improve an understanding of the animal numbers despite low numbers caught in the live-capture traps.

At Jubilee Park, 52 individuals were caught; in Wakari five possums were caught; and in Maori Hill two were caught.

In Wakari and Maori Hill, possum numbers were believed to be below one animal per hectare.

But the low densities in the two suburban areas still showed that backyards could act as habitat for possums.

Ms Patterson suggested if there were plenty of ‘‘artificial resources’’, such as compost, fruit trees and roof spaces to den in, possum numbers could be higher.

But the research showed parts of cities could harbour significant possum populations.

In order to reach New Zealand’s goal of a Predator Free 2050, control work needed to increase in cities as well as all other areas, she said.

Long-term density estimates for urban habitats should be made across a range of sites to understand possible changes in possum density due to factors such as the seasonal availability of food and timing of breeding periods, Ms Patterson said.

hamish.maclean@odt.co.nz

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