Meeting Abstract

S11.8  Friday, Jan. 7  Active control of aerodynamic forces during gliding in flying squirrels BISHOP, K.L.; BAHLMAN, J.W.*; Florida International University; Brown University joseph_bahlman@brown.edu

Early studies of gliding performance in mammals simplified aerodynamic analyses by assuming that the animals reached an equilibrium state in which there were no net accelerations on the body. In these studies only the launch and landing points were recorded and a simplified theoretical glide trajectory was assumed. Equilibrium gliding occurs when the aerodynamic forces a glider generates balance body weight, resulting in no net accelerations and constant velocity. Although this approach has improved our understanding of mammalian gliding, there is little a priori reason to believe that mammalian gliders typically use equilibrium gliding. Recent studies using high speed video of Northern and Southern flying squirrels found no instances of equilibrium conditions at any point in any observed glide trajectory under either lab or field conditions. Instead the squirrels appear to actively modulate the aerodynamic forces they generate, thereby controlling their glide trajectories, and using force coefficients that are unexpectedly high according to conventional aerodynamic theory. Although computational models suggest that flying squirrels are theoretically capable of reaching equilibrium conditions within glide distances typically traveled, their actual glide trajectories suggest that they may actively modulate their aerodynamic force coefficients to control their glide path. There are many possible ways that flying squirrels can behaviorally modulate their wing shape and orientation to actively control the aerodynamic forces they produce, and consequently modulate their accelerations and rotations about their center of mass. Our model predicts that active control of non-equilibrium gliding can greatly improve glide performance compared to equilibrium gliding.