ESSNER, R.L.: Comparison of Takeoff Kinematics in Gliding and Nongliding Squirrels

Precise descriptions of behavior are key to understanding the role of morphology in the evolution of novel locomotor modes. While a number of studies have compared morphological variation among gliding and nongliding forms, there is currently a lack of insight into the extent of variation among locomotor behaviors. This has led to questions concerning the degree of specialization necessary for gliding versus nongliding (leaping) locomotion. In order to address this concern I examined takeoff kinematics in a gliding arboreal sciurid (Glaucomys volans) and two nongliding relatives (Tamiasciurus hudsonicus, Tamias striatus). Animals were filmed launching from a 1.5-meter horizontal platform with high-speed video at 240 frames/second in lateral and dorsal views. Landmarks were digitized on the limbs, tail, and body and converted into 3D coordinates. Locomotor behavior was examined by generating kinematic profiles of angular motion at the limb joints and tail. Comparisons among the three taxa revealed similarities in the majority of kinematic parameters, indicating that takeoff behavior in these arboreal rodents is relatively conservative. Furthermore, the presumed evolutionary transition from leaping to gliding likely did not involve substantial changes related to the takeoff phase of locomotion.