Sprint Performance and Running Behavior of Obstacle Crossing in the Lizards Crotaphytus bicinctores, Gambelia wislizenii, Aspidoscelis tigris and Sceloporus occidentalis

Studies of terrestrial locomotion often focus on movement over flat uniform surfaces. In nature, animals frequently transverse many types of terrain, thus they must overcome obstacles or natural barriers such as branches, rocks, and dead wood. The ability for animals to negotiate over or around these obstacles is likely under selective pressure to successfully disperse into new habitats, acquire food, defend territories and avoid predators. Currently, studies have examined changes in locomotor performance as animals approach and cross an obstacle. In this study, four species (Crotaphytus bicinctores, Gambelia wislizenii, Aspidoscelis tigris and Sceloperous occidentalis) were used to examine locomotor performance with and without obstacles. Also, behavioral strategies (e.g. quadrupedal vs. bipedal locomotion) were examined before and after crossing an obstacle. Experimental trials took place in the field in a three-meter runway. A wooden obstacle (approximately 30% of the hindlimb length) was placed across the runway at meter 1.5. We examined the velocity, acceleration, and basic kinematics using high-speed (300 fps) video as individuals accelerated from a standstill and ran down the runway. Each individual was run three times with an obstacle and three times without. Preliminary analyses suggest no significant changes in velocity when running over an obstacle. However, behavioral strategies differ among species when crossing obstacles.