The marsh crab is a small shore crab that lives in salt and brackish marshes in the middle and lower Chesapeake Bay.
The marsh crab has a small, square carapace (shell) that grows to 1 inch wide and varies in color from warm brown to dark olive. Its eyes are on stalks located at the front corners of its body. It has two teeth toward the front on either side of the carapace and a notch along the middle of the carapace. It has furry terminal joints on its first three walking legs.
Marsh crabs are found in salt and brackish cordgrass marshes and nearby mud flats. They live communally within interconnected burrows in the mud. Burrows are 25 to 30 inches deep and are usually filled with water. Burrow entrances, which may be an inch or more in diameter, are located near the high-tide line. Marsh crabs are most active at night.
Found throughout the middle and lower Chesapeake Bay, the marsh crab ranges as far north as Arundel on the Bay near Annapolis, Maryland.
Marsh crabs eat the outermost leaves of marsh plants, especially cordgrass, and will sometimes prey upon fiddler crabs.
Black-crowned night herons are known predators of marsh crabs.
Little is known about the marsh crab life cycle. Females may carry 5,000 to 13,000 eggs at a time and breed up to five times in her lifetime.