Meeting Abstract

3.2  Tuesday, Jan. 4  The Scaling of Limb Rotational Inertia in Cursorial Mammals KILBOURNE, BM; Univ of Chicago bmkilbou@uchicago.edu

Limb shape, size, and function are known to vary widely across terrestrial mammals. However, little is known about limb rotational inertia in mammals, even though rotational inertia is a function of both size and shape. It is also unknown as to whether body size and limb function also influence the rotational inertia of limbs. To understand how limb rotational inertia is related to body size and locomotion, I examined how hindlimb rotational inertia scales with body mass across 20 mammalian species, including cursorial, scansorial, and aquatic forms. For a subset of 13 cursorial taxa, I also examined the scaling of hindlimb rotational inertia to discern whether locomotor types influence the scaling of limb rotational inertia. For the full dataset of 20 taxa, limb inertial properties (e.g., limb mass, center of mass position, moment of inertia, and natural frequency) scale according to geometric similarity, with small and large taxa having relatively equal inertial properties with respect to their body size. For cursorial taxa, limb mass scales with isometry, indicating that small and large cursors haves limb of equal mass with respect to their body. However for cursorial taxa, limb center of mass position scales with negative allometry, signifying that large-bodied cursors have hindlimbs with mass concentrated relatively proximally. In cursors, hindlimb moment of inertia and natural frequency also scale with negative allometry, suggesting that the hindlimbs of cursors are relatively easier to swing and have a lower optimal frequency of oscillation for their body size. The negative allometry of limb inertial properties suggests that as larger body and limb sizes evolved in cursorial mammals, limb rotational inertia may have had to relatively decrease to allow cursorial locomotion at larger body sizes.