Meeting Abstract

49.2  Saturday, Jan. 5  Kinetics of quadrupedal locomotion on slippery and rough arboreal trackways LAMMERS, A.R.; Cleveland State Univ., Ohio a.Lammers13@csuohio.edu

Most small quadrupedal mammals regularly encounter and move on fallen tree branches, twigs and logs. Arboreal substrates have a wide range of textures, but all studies of locomotion on arboreal substrates attempt to provide a rough texture to prevent slipping. In this study, I examine locomotor kinetics in the gray short-tailed opossum (Monodelphis domestica) as it moves on rough (60-grit sandpaper-covered) and smooth (paper-covered) arboreal trackways (2 cm diameter, about half the diameter of the animals� bodies). A 3.8 cm region of the trackway was instrumented to measure vertical, fore-aft, and mediolateral forces as well as torque around the long axis of the branch. Three video cameras recorded the manus and pes as they contacted and gripped the trackway. Preliminary data indicate that regardless of substrate texture, torque is nearly always in the same direction as the contacting limb. For example, a right limb generates a torque that would twist the top of the branch to the right, and the bottom of the branch to the left. In this example, the torque reaction should push the animal to its left. At the time of peak substrate reaction force, the torque was the same on both trackways, but torque was significantly greater in forelimbs than in hindlimbs (P=0.014). The difference may result from the greater substrate reaction forces generated by the forelimb. It is also possible, however, that the manus and pes contact the branch in different locations, or that the manus generates a twisting moment separate from the torque produced by substrate reaction forces. The interaction of autopodia contact location, substrate reaction forces, and manus/pes morphology will be explored.