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Brushtail possums (Virlda) settle into Ikara

News release
27 May 2016

Posted 31 May 2016.

It’s been nearly a year since 79 Brushtail Possums (Virlda) were translocated from the Yookamurra Sanctuary into the Flinders Ranges National Park. With more than half of those possums radiocollared, monitoring is well underway and we are beginning to learn more about their behaviours as they settle back into an area where they’ve been absent for 75 years.

Since their release radiocollared possums have been checked daily and then weekly to determine survival and habitat use. Cage traps have also been set at the base of occupied trees to catch the possums and check their health and reproductive status.

Reproduction

Although temperatures regularly exceed 40 degrees, adult possums continued to breed and maintain weight through the summer months. All females have produced pouch young with many of those now dispersed from their mothers. Observations of several collared juvenile possums by PhD student Hannah Bannister (Adelaide University) have found that they remain in the pouch for several months before being carried around on their mother’s back. They then continue to follow their mother around from tree to tree before gradually dispersing. Recently, we captured our first new Flinders born possum with her own pouch young suggesting that the next generation of possums is starting to emerge.

Behaviour, habitat and diet

Early monitoring indicates that the possums prefer to shelter in tree hollows in River Red Gum and rough-barked Coolibah trees. Diet analysis results are not yet available but the possums have been observed feeding on the leaf tips of mallee trees and on River Red Gum leaves. Range Nine of the possums have been fitted with GPS collars to track their movement. So far we have found female possums to be fairly sedentary, travelling up to 400 metres along creeklines. Male possums are more wide-ranging with distances of several kilometres reported. This is consistent with their promiscuous mating system where males find and mate with many different females.

Mortalities

Survival rates are generally high. In the last month we have seen some possums killed by cats and possibly quolls. This corresponds with late summer and a decline in rabbit numbers, a time of low food availability for predators.

Fox control

Foxes are a significant predator of possums at other release sites. Our results suggest that the fox control conducted through the Bounceback program has enabled the possums to survive after release and establish home ranges. Long term survival is now likely to depend on sufficient food resources being available, particularly during drought conditions.

The return of the Virlda to Ikara-Flinders Ranges National Park is made possible through a unique partnership between FAME and DEWNR who teamed with the Australian Wildlife Conservancy for the source population. A further reintroduction is planned in June.

Thanks to the many volunteers, contractors, donors, land managers and partners of Bounceback and FAME for their support for this project.

About the Virlda

The Brushtail Possum was once common in the rocky ranges and along creek lines in the arid interior of South Australia. Its numbers have declined since European settlement.

Prior to the introduction the most northerly populations in South Australia were found at Quorn in the southern Flinders Ranges.

In the Ikara-Flinders Ranges region, the possum – known by its Adnyamathanha name of Virlda – is thought to have become extinct in the 1940s.

Exact reasons for the decline are unknown but are likely to include predation by foxes; habitat degradation through vegetation clearance; and overgrazing by domestic and introduced herbivores.

Possums were a favoured food source for Aboriginal communities; on moonlit nights they would knock them out of trees with sticks or remove them from dens using smoke, or later, axes. Possum skins were used by Adnyamathanha as blankets while plucked fur was used to make string (Ita).

Despite being considered a pest in urban areas, possum populations are considered stable in only two regions outside of Adelaide: Kangaroo Island and the South East.

Stop Press

Donors and dignitaries gathered at Wilpena Pound in early May as 15 additional Western Quolls (Idnya) flew in from Western Australia for release into the Ikara-Flinders Ranges National Park in May.

They join an estimated 150 quolls now in the area which includes second and third generation individuals.

This was the third and final release of quolls as part of this ambitious reintroduction project which brought together the Department of Environment, Water and Natural Resources, Foundation for Australia’s Most Endangered Species, and WA Department of Parks and Wildlife.

Monitoring will continue for another two years to assess whether the quolls have been able to establish a sustainable population and we will bring you news on how they are faring in a future edition

SA Arid Lands NRM Board, DEWNR, Foundation of Australia's Most Endangered Species, Ecological Horizons

Article originally published in Across the Outback (May 2016) by Katherine Moseby, Ecological Horizons

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