Fiddler crabs are small crustaceans with a distinctive enlarged claw. They live on beaches, mud flats and marshes throughout the Chesapeake Bay.
Three species of fiddler crabs can be found in the Chesapeake Bay region:
Fiddler crabs vary in color from tan to brown. Sand fiddler crabs are lighter than the other two species. Males have one enlarged claw that can grow to 1.5-2 inches long while females’ claws are equal size. The carapace (shell) is squared with rounded rear edges. The red-jointed fiddler crab’s carapace has a groove behind each eye. Male marsh fiddler crabs have a royal blue spot on the center of the carapace, while male sand fiddler crabs have a blue or purplish carapace. Carapace varies in size from less than an inch wide to 1.5 inches wide. The marsh fiddler crab is the smallest fiddler crab in the Bay region and the red-jointed fiddler crab is the largest. Fiddler crabs have four pairs of walking legs
Generally found in marshes, beaches and mud flats. Red-jointed and marsh fiddler crabs live in muddy areas in marshes. Red-jointed fiddler crabs are more tolerant of low salinities. Marsh fiddler crabs are found between the low and high tide lines, while red-jointed fiddler crabs dig burrows above the high-tide line. Sand fiddler crabs live on sandy, salt and brackish beaches and flats. Unlike the other two fiddler crab species, sand fiddler crabs cannot survive in muddy areas because they can only feed over sediment particles of a certain size.
Fiddler crabs create tiny, sometimes elaborate burrows for mating, sleeping, refuge, and “hibernating” during winter. Burrows can be 2 feet deep. They are very active during the day and return to their burrows at night and during high tide, plugging the entrance with mud or sand.
Found throughout the Chesapeake Bay region. Red-jointed fiddler crabs range into the upper Bay, while marsh and sand fiddler crabs are generally restricted to the middle and lower Bay.
Fiddler crabs eat algae, bacteria and decaying marsh plants. They feed by sifting through sand or mud for food particles.
Fiddler crabs mate every two weeks in summer. Males dig, maintain and defend a tidy, cylindrical burrow. To find a female partner, males stand next to their burrow while females walk past. The males wave their major claw to attract a female’s attention. If a female is interested, she will stare at a male for a short period of time. The male then runs toward the female and runs back to his burrow. He repeats this motion several times until the female either moves on or follows him. If the female follows, the male drums the edge of the burrow with his claw, then leads the female inside, plugs the entrance and returns to the female to mate. Females incubate their egg sponge for two weeks before returning to the surface. They release the eggs into the water, where they hatch and develop into juveniles.
Fiddler crabs molt once or twice per year. During the soft-shelled period, fiddler crabs remain in or near their burrow.