FRANZ, T.M.*; DEMES, B.; CARLSON, K.J.; Stony Brook University; Stony Brook University; Stony Brook University: The kinetics of leaping in strepsirrhine primates

This study explores the forces associated with leaping in two primate species and how they compare to forces of nonprimate mammals performing similar tasks. Takeoff and landing forces were analyzed for two species of strepsirrhine primates, Lemur catta (n=3) and Eulemur fulvus (n=3), performing running jumps of 0.5 – 2 m distances. Vertical and horizontal peak forces and impulses were collected in an experimental setup consisting of a force plate at ground level and a raised platform of 0.5 m height. For both species, peak vertical forces and impulses tend to be greater at landing than at takeoff, and forces increase with distance leapt. Vertical peak forces do not exceed 3 times weight force. For L. catta, vertical forces and impulses are significantly greater for the hind limb at both takeoffs and landings. E. fulvus produces significantly higher peak vertical forces with the hind limbs at takeoffs, but the forelimb forces tend to be higher at landings. Nonprimate mammals consistently generate higher forces with their forelimbs. Both braking and propulsive forces were low in comparison to vertical forces, even for the longest jumps. Animals generate forward impulse in a run-up and just redirect the velocity vector at takeoff to gain the requisite height to reach the elevated target platform. Similarly, some of the horizontal impulse at landing is carried into a run-out. Our data are consistent with the idea that primates, being an arboreal radiation in a fine branch niche, adopt movement patterns that keep substrate forces low, and partially support previous findings of hind limb dominance in primate locomotion. Supported by NSF BCS0109331