Fiddler crabs are small, semi-terrestrial marine creatures found in marshes and sand flats throughout the Chesapeake Bay. They have four pairs of legs and their carapace is squared with rounded rear edges. Males have an oversized claw which is used to attract mates and to discourage rivals, while the claws of female fiddler crabs are small.

There are three species common to the Chesapeake Bay. The red-jointed fiddler lives in muddy and brackish water marshes and is the most common. The mud fiddler is found in inter-tidal areas and is smallest of the three species. The sand fiddler crab is lighter in color and lives on sandy, flat beaches.

Fiddler crabs create tiny, elaborate burrows for mating, sleeping, seeking refuge from predators and hibernating during the winter. They are very active during the day, searching for food and digging burrows. They return to their burrows at night, barricading the entrance with mud or sand. In summer, they are busy mating every two weeks.

Fiddler crabs feed on algae, bacteria and decaying marsh plants. They eat by picking up sediment and scraping it with their mouths to remove food particles. Females are better able to do this than males because their claws are small and dexterous.