Physics elucidates sand-burrowing lizards’ motion

Science News : By using a combination of computer simulation and lizard-mimicking robots, Daniel Goldman of Georgia Tech and his colleagues have determined how the sandfish lizard is able to burrow at a maximum rate of two body lengths per second through a sandy medium. Optimization of the lizard’s wiggling motion is the key. The bigger the amplitude of the lizard’s wiggles, the more force the lizard exerts on the sand. But that increased force, being side to side, doesn’t yield faster forward motion. A medium wiggle is optimal. The problem of determining the sandfish lizard’s motion reflects the challenges of understanding granular media, which share some properties with solids and others with liquids. Goldman’s paper is scheduled to appear in the journal Royal Society Interface.