Use of Tree Hollows by Two Sympatric Gliding Possums, The Squirrel Glider, Petaurus norfolcensis and The Sugar Glider, P. breviceps.

Populations of the Squirrel Glider, Petaurus norfolcensis and the Sugar Glider, P. breviceps, are often sympatric and the two species are potential competitors for tree hollows. Their use of hollows and artificial nest-boxes was examined in a Box-Ironbark forest where natural hollows are scarce due to past forestry practices. We found gliders used hollows in the boles and branches of trees and in coppicing stumps. There was considerable interspecific overlap in the use of hollows and nest-boxes, both by gliders and other birds and mammals. Both gliders preferred hollows and nest-boxes with narrow entrances (<50 mm diameter). Petaurus breviceps preferred nest-boxes and possibly natural tree hollows with entrances too narrow for the larger P. norfolcensis. When abundant nest-boxes of this type were introduced at the study site, P. breviceps numbers increased and then decreased when the nest-boxes were removed. The results suggest that the larger P. norfolcensis monopolise the best available hollows. Petaurus breviceps numbers may have been limited by a lack of suitable hollows.