The sand crab lives under the surface of the sand, moving up and down the beach according to the state of the tide.
As each wave advances and retreats, the crab comes to the surface and extends its antennae to feed.
This makes it vulnerable to predatory birds such as the sanderling.
These birds actively patrol the part of the beach washed by incoming waves, probing the softened sand with their bills.
The sand crab retreats under the sand surface as each wave goes out, maximizing its chance of being out of reach of the bird's beak.
The bird maximizes its chance of feeding on sand crabs by scurrying at the edge of the surf.

Other birds that eat sand crabs include willets, godwits, surf scoters, blackbellied plovers, and curlews.
The sea otter also consumes them.
The crabs are hosts to the intermediate stages of various parasitic worms.
These are passed on to predators when the predators eat the crabs, and if enough worms are ingested, they have been known to kill the predator.

The barred surfperch (Amphistichus argenteus), found off the coast of California, consumes a large number of sand crabs.
Surf fishermen use the crabs for bait and commercial bait fisheries extract them from the beach.
The sand crabs with soft shells that have just moulted are kept for bait, while the hard-shelled crabs are thrown back into the sea.

The sand crab has been evaluated as an indicator species for monitoring the level of domoic acid-synthesizing diatoms (Pseudo-nitzschia spp.)
which sometimes cause toxic blooms off the coast of California.
The sand crab lives under the surface of the sand, moving up and down the beach according to the state of the tide. As each wave advances and retreats, the crab comes to the surface and extends its antennae to feed. This makes it vulnerable to predatory birds such as the sanderling. These birds actively patrol the part of the beach washed by incoming waves, probing the softened sand with their bills. The sand crab retreats under the sand surface as each wave goes out, maximizing its chance of being out of reach of the bird's beak. The bird maximizes its chance of feeding on sand crabs by scurrying at the edge of the surf.
Other birds that eat sand crabs include willets, godwits, surf scoters, blackbellied plovers, and curlews. The sea otter also consumes them. The crabs are hosts to the intermediate stages of various parasitic worms. These are passed on to predators when the predators eat the crabs, and if enough worms are ingested, they have been known to kill the predator.
The barred surfperch (Amphistichus argenteus), found off the coast of California, consumes a large number of sand crabs. Surf fishermen use the crabs for bait and commercial bait fisheries extract them from the beach. The sand crabs with soft shells that have just moulted are kept for bait, while the hard-shelled crabs are thrown back into the sea.
The sand crab has been evaluated as an indicator species for monitoring the level of domoic acid-synthesizing diatoms (Pseudo-nitzschia spp.) which sometimes cause toxic blooms off the coast of California.
Emerita analoga