HYDE, Martha L.*; PARRA, Laura G.; West Texas A&M Univ., Canyon; West Texas A&M Univ., Canyon: Theoretical Aspects of Bipedal Locomotion in Kangaroo Rats: Comparison of Field and Laboratory Locomotion with Respect to Neural Control Mechanisms

Infrared films (taken with a PC164C-EX Infrared camera and CML4IR Intelligent IR Lens, Supercircuits, http://www.supercircuits.com/) of bipedal locomotion in kangaroo rats, Dipodomys ordii were used to obtain normal feeding locomotor behaviors of kangaroo rats in the field (Alibates Quarry, Texas). The filming arena included a 100 cm x 50 cm x 50 cm wooden frame with bicycle reflectors at 10 cm intervals on each of the three axes, placed on open areas of a dirt road, near vegetation. Locomotor parameters measured included: stride length, jump height, stride time, angle of projection, and velocities, and accelerations of individual joints (toe, ankle, knee). We treated the kangaroo rat as a simple projectile and modeled the motion using initial parameters of the measured angles of projection, initial body velocity, and an average body mass of 49.6 g (taken from museum specimens of these species). Most movements of the kangaroo rat were significantly different from the predicted values, suggesting that motivational differences may alter many components of limb and body movements. Since some predicted values varied significantly from measured values, we hypothesized that characteristics of the soil may affect locomotion. Traction on fine sand may strongly affect parameters such as stride length and jump height, thus leading the animal to greatly alter its angle of projection in order to achieve the speeds, stride lengths and jump heights desirable for eluding predators or achieving an energetically efficient method of feeding. The study was partially funded by West Texas A&M University and the Ronald E. McNair post-baccalaureate achievement program.