The marsh crab has a small, square carapace (shell) that varies in color from warm brown to dark olive. (The Southeastern Regional Taxonomic Center, South Carolina Department of Natural Resources)
The marsh crab has a small, square carapace (shell) that varies in color from warm brown to dark olive. (North Carolina State Parks Natural Resources Inventory Database)
The marsh crab is a small shore crab that lives in salt and brackish marshes in the middle and lower Chesapeake Bay.
Appearance
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.
Feeding
Marsh crabs eat the outermost leaves of marsh plants, especially cordgrass, and will sometimes prey upon fiddler crabs.
Predators
Black-crowned night herons are known predators of marsh crabs.
Reproduction and Life Cycle
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.
Did You Know?
- The marsh crab is also known as the purple marsh crab, the square-backed marsh crab and the heavy marsh crab.
- Males are known for making “rapping” sounds when defending their burrow.
- They have been linked to large losses of cordgrass in marshes on Cape Cod, Massachusetts, due to overeating.
Sources and Additional Information
- A Field Guide to the Atlantic Seashore by Kenneth L. Gosner
- Life in the Chesapeake Bay by Alice Jane Lippson and Robert L. Lippson
- Crustacea of New Jersey from the 1911 Annual Report of the New Jersey State Museum
- Animals of the Seashore by Horace G. Richards
- Beachcomber’s Guide to Gulf Coast Marine Life by Susan B. Rothschild
Quick Facts
Species
Native
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Habitat
Found in salt and brackish cordgrass marshes and nearby mud flats. Lives communally within interconnected burrows in the mud. Burrows are 25 to 30 inches deep and usually filled with water. Burrow entrances, which may be an inch or more in diameter, are located near the high-tide line. Most active at night.
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Range
Found throughout the middle and lower Chesapeake Bay, ranges as far north as Arundel on the Bay near Annapolis, Maryland.
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Diet
Feeds on the outermost leaves of marsh plants; sometimes preys upon fiddler crabs
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Status
Stable
