Meeting Abstract

70.2  Tuesday, Jan. 6  Scaling of flight characteristics in bats SWARTZ, SM*; RISKIN, DK; IRIARTE, J; MIDDLETON, KM; BREUER, KS; Brown University; Brown University; University of Chicago; California State University, San Bernardino; Brown University sharon_swartz@brown.edu

The more than 1200 living bat species range in body size from 2 g to >1,500 g but share a single pattern of wing architecture: all possess flexible skin membranes supported by elongated digits. We sought to determine how the inertial costs of flight scale with body size among six species differing 45-fold in body mass, selected from the Pteropodidae, a single lineage of bats. Under isometry, the moment of inertia of a wing should scale with body mass^5/3. If wing kinematics are conserved across species, this would result in an increased inertial power per kilogram body mass for larger bats than for smaller ones. Bats were videographed at 1000 Hz, and the positions of 17 kinematic markers on the body and one wing were resolved in three dimensions. By modeling the wing as a set of 31 topologically linked point masses, we use the high-resolution kinematics to model the dynamics of wing inertia. Wing moment of inertia of a wing changes by as much as 70% during a wingbeat cycle. Both fine-scale kinematics and wingbeat frequency vary systematically with body size, but these two parameters vary inversely in such a manner that mass-specific inertial power during flight is independent of body size. This pattern differs from that observed in terrestrial mammals, and could indicate a fundamental constraint on the design of the bat flight apparatus.