Gliding patterns of Siberian flying squirrels in relation to forest structure

Abstract: It is widely accepted that the evolution of gliding ability is correlated with forest environments, but differences in gliding locomotion in relation to forest structure remains poorly elucidated in mammals. Although the cost of gliding locomotion decreases with increasing glide distance per unit vertical drop (glide ratio), gliding mammals often use costly low-ratio glides and seldom exploit maximum-ratio glides. In this study, we evaluated our hypothesis that low-ratio glides are related to forest structure by measuring glide distance, vertical drops and landing tree heights in Siberian flying squirrels (Pteromys volans), and we also recorded their behaviour in landing trees. Glide ratio decreased with increasing landing tree height. Squirrels landed on taller trees using low-ratio glides and tended to depart from them quickly without spending much time there, but used high-ratio glides to land on shorter trees for foraging or nesting. Thus, flying squirrels use two different gliding behaviours depending on their immediate objective, where inefficient low-ratio glides are used to move to higher trees for continued gliding. This approach might be necessary for efficiency and safety in subsequent glides, because taller trees facilitate long-distance glides and significantly decrease energy costs and landing impact. Therefore, the location of tall trees in forests and/or average canopy height might alter glide path routes. This study provides important evidence that forest structure affects gliding patterns and provides insight on how forest management could influence the gliding locomotion of Siberian flying squirrels.