Meeting Abstract
42.6 Tuesday, Jan. 5 How do bats accelerate? RISKIN, DK; IRIARTE-DíAZ, J; MIDDLETON, K; BREUER, KS; SWARTZ, SM*; Brown University; The University of Chicago; California State University San Bernardino ; Brown University; Brown University sharon_swartz@brown.edu
Analysis of the wing kinematics of bats flying at constant speed has provided understanding of mechanisms of thrust production. In contrast, the kinematic correlates of acceleration have not been studied for any bats, although such data would provide further insight into aeromechanics. Horizontal accelerations should be good indicators of thrust production, and vertical accelerations should reflect lift production. We studied the flight kinematics of 28 pteropodid bats, spanning six species and a 45-fold range in body masses to determine the influences of flight speed (Vhoriz), horizontal acceleration (Ahoriz), and vertical acceleration (Avert) on wing kinematics. Bats were painted with 17 reflective markers on the body and one wing, then flown in a wind tunnel or flight corridor, and filmed with three phase-locked high-speed cameras. A single wingbeat cycle was isolated from each of five separate flights for each individual. For each of several kinematic parameters, we used multiple regression analyses to quantify the influences of Vhoriz, Ahoriz, and Avert on that parameter. Those analyses were done separately for each of the six species. We found that as Vhoriz increased, bats exhibited decreased wing extension, decreased wingbeat frequency, decreased stroke plane angle, decreased angle of attack, and decreased camber. As Ahoriz increased, bats increased wing extension, amplitude, and angle of attack, and decreased stroke plane angle. As bats increased Avert, they increased wing extension, wingbeat frequency, angle of attack, and camber. Each of these changes was significant in one or more species, and no species showed any trend opposite those seen in other species. These results provide a clear picture of how thrust and lift are produced by bats, and demonstrate that these trends are robust across a broad range of body sizes.
