Meeting Abstract

71.5  Wednesday, Jan. 6  Bat flight and hierarchies of variability HUBEL, T.Y.*; HRISTOV, N.I.; RISKIN, D.K.; SWARTZ, S.M.; BREUER, K.S.; Brown University tatjana_hubel@brown.edu

Kinematics as well as morphology differ greatly among the approximately 1200 living species of bats, and it is crucial to understand the effects that the body, wing shape and pattern of wing movement have on wake structure. One key aspect of this subject is to understand the relative magnitude of variation in kinematics and aerodynamics among the wing beats of individuals, among individuals of the same species and among different species. To answer this question, we investigated the aerodynamics and kinematics of multiple individuals of three bat species over a range of flight speeds. Based on the overall patterns of kinematics observed during bat flight to date, we predicted that the wakes of all bat species should develop discrete vortex rings, and generate negative circulation in the wing tip area at the end of the downstroke. We tested this hypothesis in three species of bats: Cynopterus brachyotis (Pteropodidae), Tadarida brasiliensis (Molossidae), and Myotis velifer (Vespertilionidae). These species vary in their ecology regarding foraging, roosting preferences, and migration habits, and have associated differences in morphology, including aspect ratio, wing shape and wing loading. We used PIV to visualize the wake structure and quantify vortex generation over multiple wing beat cycles. Simultaneously, we recorded the wing motions using three high-speed cameras in order to link the kinematics directly to the forces generated on the wing. Our results reveal that wake structure varies among species, and changes over a range of wind speeds. This pattern suggests that bats employ a more flexible strategy that includes variation among species in the details of force production in relation to the specifics of wing form and kinematics, and modulating force production mechanisms with changing velocity.