The occurrence of gliding possums in old-growth forest patches of mountain ash (Eucalyptus regnans) in the Central Highlands of Victoria

The montane forests of the Central Highlands, Victoria, are managed for multiple uses that include biodiversity conservation and timber harvesting. Old-growth communities within mountain ash forest have been shown to support a range of fauna. These communities have a restricted distribution, as a result of combined effects of previous wildfires and timber harvesting. Patches of mountain ash old-growth forest vary in size, shape, topographic position, structure, and isolation from other patches. The study investigated effects of this spatial patterning on selected fauna that require old trees. Arboreal marsupials were used to measure these effects, focusing on the yellow-bellied glider (Petaurus australis) and the greater glider (Petauroides volans). Forty-nine old-growth forest sites were surveyed for gliders using spotlight transects and owl-call playback, and for a variety of landscape and habitat variables. Occurrence of the greater glider was significantly related to overstorey basal area (P<0.001). An alternative model found greater glider occurrence to be significantly related to old-growth patch size (P=0.004). The probability of yellow-bellied glider occurrence was highest at sites located in large patches of old-growth forest (P=0.03). These results appear to be related to the foraging requirements and population biology of the yellow-bellied glider and shelter requirements of the greater glider. The abundance of greater gliders at a site was also found to be significantly related to overstorey basal area (P<0.001). The size and quality of old-growth forest patches (quality measured by overstorey basal area) were shown to influence their value for fauna conservation.