21.3 Sunday, Jan. 4 14:00 Shaping the wings of bats: Muscle and wing skin interactions in flight CHENEY, J A*; KONOW, N; MIDDLETON, K M; BREUER, K S; ROBERTS, T J; GIBLIN, E L; SWARTZ, S M; Brown University, Providence, RI; Brown University, Providence, RI; University of Missouri, Columbia; Brown University, Providence, RI; Brown University, Providence, RI; Brown University, Providence, RI; Brown University, Providence, RI Jorn_Cheney@Brown.edu
Bat wing membranes are extremely thin. Because of the structural slenderness of the membrane and its composition of compliant skin, it has little bending stiffness, which results in the wing membrane supporting aerodynamic load primarily through tension. To bear aerodynamic load through tension, the wing membrane deflects and its three-dimensional configuration changes, forming an aeroelastic coupling between membrane stiffness and aerodynamic force. This coupling can confer many potential benefits, but has the notable consequence that there is a limited range of aerodynamic conditions in which the membrane performs optimally. Bats possess an array of muscles that both originate and insert into the wing membrane that have been hypothesized to extend this range of optimal flight mechanics by modulating wing membrane stiffness. We measured the electromyogram of the plagiopatagiales proprii in flight in Jamaican fruit bats, Artibeus jamaicensis, at two flight speeds. We found that the muscles contract synchronously during downstroke, which is likely to maximize force production. Our results indicate that the coordinated function of the plagiopatagiales proprii may act to modulate wing stiffness in flight and therefore also three-dimensional wing form.