Meeting Abstract

8.4  Jan. 4  Maneuvering Obstacles on a Treadmill by Hopping Kangaroo Rats, Dipodomys ordii HYDE, Martha L.; West Texas A&M Univ, Canyon mhyde@mail.wtamu.edu

The unpredictability of kangaroo rat locomotion is remarkably adapted to predator avoidance. Neural control mechanisms may allow for these rodents to effectively elude predators and still maneuver in a habitat that can be seasonally littered with annual and perennial plants of various sizes. Four kangaroo rats, Dipodomys ordii, were videotaped on a custom-designed Columbus Instruments treadmill bed 97×45 cm with a plexiglass box (111x31x30 cm). The box was modified to accommodate polyurethane foam obstacles attached with Velcro to the treadmill belt. The obstacles traveled the full length of the treadmill bed while animals hopped. The box was further modified to maintain a minimum distance of 40 cm between rodent and first appearance of an obstacle on the belt. The rodents were videotaped at 30 fps with three cameras for a dorsal view, a side view with closeup, and a side view with full view of the treadmill. All kangaroo rats responded to the first introduction of one 26×3.5×4 cm obstacle at 1.30 mps belt speed in the same way: they paused, the belt carrying them to the rear of the box. Responses thereafter varied from jumping to climbing to moving to the side of the obstacle. All continued to hop afterward in that first run but stayed in the back of the box. Subsequent introduction of obstacles either one at a time at 1.30 mps or multiple obstacles on the belt when it started at 1.00 mps produced varied responses. All animals adapted very quickly to the obstacles within three-four turns of the belt, as seen in more predictable angles of projection, timing of jump, jump height and stride lengths. These animals probably know the placement of all obstacles within their territory pretty soon after dispersal, maintaining unpredictability to predators and avoiding crashing into these obstacles.