Gliding performance and its relevance to gap crossing by the squirrel glider (Petaurus norfolcensis)

Gliding mammals occur worldwide and many are subject to increasing levels of habitat fragmentation. Knowledge of their ability to cross tree-gaps by gliding is quite poor. We describe aspects of the gliding performance of the squirrel glider (Petaurus norfolcensis) based on recorded parameters of 85 glides of 73 individuals. Animals launched from a horizontal position similar to 1.7m below the top of a tree and 2.3m out from the main trunk. All but one glide was to the trunk of a tree, landing 5.7m above the ground. Animals glided a mean of 21.5 +/- 0.9m( range 9-47 m) in a horizontal plane, with no significant difference between the sexes. Horizontal glide distance appears to reflect tree spacing where individuals were released. The mean glide angle was 28.5 +/- 0.8 degrees, with no significant difference between the sexes. We predict that trees beside roads that create a tree-gap of 20m (two-lane road) or 43m (four-lane road) will need to be a least 13m and 25m tall, respectively, to enable animals to safely glide across a road. Where trees are absent, 12-m-high wooden poles could be installed, requiring some in the median strip of four-lane roads.