IRIARTE-DIAZ, J.*; LEE, M.-M.; Brown University; Brown University: Kinematics of slow turning maneuvering in bats

Maneuverability is an important feature for flying animals as they need make turns to capture prey or move around in their environment. The fundamental mechanism used to maneuver during flight is the asymmetrical generation of aerodynamic forces by the wings. This asymmetry could be produced in several ways (e.g., by differential downstroke velocities, by changes in the angle of attack and camber, or by altering the surface area of the wings by flexing the elbow and/or wrist). How different animals use these mechanisms to maneuver, however, is not well understood. The purpose of this study is to describe the kinematics of turning in the lesser short-nosed fruit bat (Cynopterus brachyotis) to infer the mechanisms involved in its maneuvering. Two individuals were trained to fly in a L-shaped flight enclosure making a 90-degree turn midway through each flight. Flights were recorded with three high-speed video cameras allowing us to reconstruct the 3D kinematics of the body and wings during a turn. As has been observed in pigeons, bats showed differential downstroke wing velocities but contrary to what was expected, the inside wing relative to the turn showed higher downstroke velocities than the outside wing. We found no differences in the extension of the wings during downstroke suggesting that bats do not modify their wing surface area. Both wings were moving in-phase at the end of the upstroke, but during the downstroke they became out-of-phase and the wings moved briefly in opposite directions (i.e., the inside wing upward and the outside one, downward). This suggests that, if the upstroke is able to generate downward aerodynamic force, the two wings together could produce a rolling moment during part of the wingbeat.