Meeting Abstract

44.3  Wednesday, Jan. 5  Turning the corner in arboreal locomotion: the kinetics of changing direction in the Siberian chipmunk (Tamias sibiricus) LAMMERS, A.R.*; SUFKA, K.M.; Cleveland State University; Cleveland State University a.lammers13@csuohio.edu

Arboreal animals frequently change directions during locomotion on tree branches, trunks, or twigs. The linear and rotational impulses required to change direction during locomotion on a bent branch are largely unexplored. We measured substrate reaction forces and yaw torque from Siberian chipmunks (Tamias sibiricus) running on two cylindrical trackways 2 cm in diameter. The first trackway was straight with a force pole positioned in the middle. The second trackway had a 45° bend to the right with a force pole positioned before the bend; the chipmunks then ran on the same track in the opposite direction to collect force data after the turn. Speed was lower on the bent trackway, although braking and propulsive impulses were unaffected. During the turn the chipmunks exerted strong impulses to the left, which pushed the body to the right. Before and after the turn, opposite yaw angular impulses were exerted to begin and end rotation of the body toward the new heading. We conclude that mediolateral forces are more important than craniocaudal forces to change direction in locomotion. Forelimbs are typically the limb pair that drives any change in direction, although hindlimbs also contribute. Comparative data from quadrupeds are scant, but it is possible that these are general patterns. The yaw torques required to rotate the body are most likely exerted via a force couple between right and left limbs, with no difference between fore- and hindlimbs.