The survival of leadbeater's possum
To read New Restoration Forest Management Prescriptions to Conserve Leadbeater’s Possum and Rebuild the Cover of Ecologically Mature Forest in the Central Highlands of Victoria. If you can't access the document please call +61 2 6125 7800 for an email copy.
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Leadbeater's possum was first described in 1867 from dense tea-tree thickets around the Bass River east of Melbourne. By the early 1900s no further animals had been found and the land around the Bass River was extensively cleared, so the possum was thought to be extinct.
Almost 100 years after the first specimens were collected, and 50 years after it was last seen, the possum was 're-discovered' in 1961, near Marysville in the Central Highlands of Victoria. This new location was dominated by Alpine Ash - very different to the tea-tree thickets the possum was first discovered in.
The entire known distribution of leadbeater's possum now falls almost entirely within the montane ash forests in Central Victoria, with small populations also occurring in Snow Gum (Eucalyptus pauciflora) forest and lowland swamp forest at Yellingbo Nature Conservation Reserve.
Models assessing the current and predicted abundance of leadbeater's possum indicated a massive decline in leadbeater's possum numbers between the present and the year 2020 due to a decline in tree hollows, followed by a population bottleneck lasting until the year 2075.
This predicted 'bottleneck' means that for a period of 55 years, from the year 2020 to 2075, habitat suitable for leadbeater's possum, and by implication population size, will be at its lowest. Population Viability Analysis conducted by Lindenmayer and others indicated that genetically stable populations can exist in areas as small as 600ha.
Researcher, Dan Harley, has recently completed a PhD (Monash Uni) on the isolated Yellingbo Nature Conservation Reserve population of leadbeater's possum. He found a number of differences in habitat use compared to the possums living in the ash forests, such as their ready use of nest boxes and their diet of paperbark, tea-tree and eucalypt sap rather than wattle sap.
A recovery plan (DEH) has been written for leadbeater's possum, outlining the planned recovery process.
Efforts have been put into place to protect this endangered possum from the negative effects of logging. 25 Leadbeater's Management Units have been, or will be defined, with specific management for the possum, and which will contain some permanent reserve areas.
There are no longer any leadbeater's possums held in captivity. The last captively held animal died at Healesville Sanctuary in May 2006. There is effectively no back-up population at this stage.
Recent research by David Lindenmayer and team (Ross Cunningham, Damian Michael and Lachie McBurney, with DSE) has begun on a novel management system of combined logging and habitat retention, called Variable Retention Harvesting. This system utilises leadbeater's preference for a combination of old trees with hollows and new-growth forest.
Either 3 plots each 0.5ha, or a single 1.5ha plot will be retained in a logged coupe. The plots will contain an optimal combination of old hollow bearing trees with not-so-old trees that will contain hollows in the future. This research is still young and no results are available at this stage.
Successful management for the long-term conservation of leadbeater's possum has clear benefits to a wide range of other hollow-dependent fauna inhabiting the montane ash forests of Victoria.
The survival of leadbeater's possum hinges on our ability to develop ecologically sustainable logging practices.