ESSNER, R. L.; Ohio University, Athens: Fluttering: A novel locomotor behavior in flying squirrels

Aerial locomotion in mammalian gliders has never been fully investigated using the techniques of high-speed video and three-dimensional kinematic analysis. Consequently, descriptions of gliding behavior have remained relatively simplistic. This study quantifies limb and tail movements during the airborne phase of flying squirrels (Glaucomys volans) and compares them with nongliding relatives, red squirrels (Tamiasciurus hudsonicus) and chipmunks (Tamias striatus). Following the launch, nongliding squirrels initiated gradual protraction and abduction of the limbs in a symmetrical manner. In contrast, flying squirrels initiated highly stereotyped fluttering movements characterized by a series of rapid asymmetrical rotations, involving simultaneous rolling (abduction/adduction) and yawing (protraction/retraction) limb movements. Rolling was initiated by rotating the anterior and posterior limbs in opposing directions about the long axis of the body; while, yawing involved sweeping opposing sets of ipsilateral limbs either forward or backward. Initial rotations were followed by counter-rotations that were repeated numerous times with decreasing amplitude, until they eventually attenuated into a fixed gliding posture. This complex sequence of rotations and counter-rotations is hypothesized to be a novel behavioral mechanism in flying squirrels for dealing with residual angular momentum imparted by the launch and may also represent a mechanism for controlling stability.