Meeting Abstract
Locomotor performance of all organisms depends on the interaction between an organism and its environment. Granular substrates are common in many environments. These materials can act both as a solid and a fluid when disturbed by moving organisms. A wide diversity of terrestrial animals run on, or burrow into granular substrates. In a granular substrate, small particles are displaced when disturbed. Displacement of these particles during running leads to wasted energy accelerating sand particles rather than the running animal. This has the potential to negatively impact running performance. Particle size may play an important role in this process because smaller, and therefore lighter, particles may be accelerated more easily, making locomotion more difficult for animals. Particle shape may also be an important factor because this determines how individual particles will pack together and, therefore, affect the load bearing capacity of the substrate. We tested for effects of particle size and shape on the performance and kinematics of the Steppe Runner lizard (Eremias arguta). We measured sprinting performance on six substrates composed of glass spheres varying particle diameter and six natural sand substrates varying average particle size and also particle shape. Our results show that performance is inhibited both by very small and very large particle sizes, with maximum performance observed on intermediate sizes. If particles are too small then too much of the lizard’s energy is wasted by accelerating particles, resulting in decreased acceleration of the lizard. However if particles are too large, then the lizard’s kinematics are affected by the uneven surface of the substrate, resulting in decreased average velocity. This suggests that optimal substrates for running are a balance between two opposing substrate characteristics.
