Emerita analoga - commonly known as the sand crab or mole crab - dominate the sandy beaches of Southern California, populating the coasts of North and South America. They inhabit wash zones by migrating with the tide, maintaining a certain level with the breaking waves so that water will flow through their food-filtering antennae for the maximum amount of time for efficient feeding (MacGinitie 1938). Their migration and burrowing behavior depend on the characteristics of the sand and of the waves washing the sand-- they will burrow out when they get too close to the lower boundary - dilineated by the area of breaking waves - "ride" the waves to burrow further up the beach, and burrow out again when they reach the upper thixotrophic zone (fluid-like sand), this time riding with the back-wash of the waves down the beach (Cubit 1968). Not only does staying within the boundaries of the wash zone assist with feeding, but also allows them to escape predation from birds higher along the beach and predatory fishes further down the beach.
