Den trees, hollow-bearing trees and nest boxes : management of squirrel glider (Petaurus norfolcensis) nest sites in tropical Australian woodland

The squirrel glider (Petaurus norfolcensis) is an arboreal marsupial potentially impacted throughout its geographic range by the loss of hollow-bearing trees. We investigated the use of den trees and the availability of hollow-bearing trees near Mackay in the tropical north of the squirrel glider range where information was deficient. Mean den tree size (41.1 ± 2.9 cm (s.e.), diameter at breast height (dbh)) was significantly larger than that of available trees (27.5 ± 0.9 cm). Dead trees (stags) comprised 52% of 27 dens but comprised only 12% of available trees. This likely reflects the greater frequency of hollows in dead trees compared with other trees. Surveys found that 59% of 720 available trees contained hollows. A much lower percentage of trees in the 10–30-cm dbh size class were hollow-bearing (22%) compared with trees >30 cm (77%), and we view these smaller trees as those providing future den trees. Their density varied from 17 to 95 ha–1 among sites, which suggests that most sites have an adequate supply of future hollows. We installed 56 nest boxes to determine use by squirrel gliders. Only 20% were used after 3 years, but use was not influenced by the availability of tree hollows. Tree hollow availability appears adequate for the squirrel glider in these tropical woodlands but further studies are needed to understand the dynamic processes that govern this resource.