Meeting Abstract

59.5  Saturday, Jan. 5  The effect of loading on flight kinematics of bats: a case of kinematic plasticity IRIARTE, J.**; RISKIN, D.K.; SWARTZ, S.M.; Brown University; Brown University; Brown University jose_iriarte@brown.edu

All bats experience daily and seasonal fluctuation in body mass. Presumably, an increase in mass requires changes in flight kinematics to produce the extra lift necessary to compensate for the increased weight. How bats modify their kinematics to increase lift, however, is not well understood. In this study we investigated the effect of added mass on flight kinematics for bats flying between 2.6 and 8.5 m/s. Three lesser short-nosed fruit bats (Cynopterus brachyotis) were trained to fly in a wind tunnel with and without a load of ca. 20% of original body mass. Reflective markers were placed on the body and wings and flights were recorded with three synchronized, high-speed digital video cameras. Data from the three cameras were combined to reconstruct the 3D motion of each marker, from which we calculated wingbeat frequency, wingbeat amplitude, angle of attack, and wing joints extension. Each individual bat showed highly significant and systematic differences in kinematics between unloaded and loaded treatments. However, the specific response was different for each individual. For example, frequency was higher in the loaded condition than in the unloaded one for two individuals, but the third showed no difference. Other parameters showed similar differences between individuals. This indicates that bats are able to increase lift in different ways, and that not all individuals choose to increase lift the same way. Our results caution the use of simple aerodynamic models to evaluate flight characteristics of bats. Where possible, we recommend that variation among individuals should be measured when analyzing complex locomotion, such as the flight of bats.