Hobbies And Interests
Physical Traits
Fiddler crabs have square shells, eight legs and two claws. Their eyes are located on two slender stalks in the middle of their shells. The male uses his giant claw for attracting mates, fighting off strangers, and settling territorial boundaries with his neighbors. The second claw is much smaller and used for feeding. Females have two small claws used for feeding. Males are typically brighter in color than females, with purple or blue shells and brown or black markings. The giant claw is typically a contrasting color to the shell. Fiddler crabs are amphibious and although they have gills for breathing underwater they also have a primitive lung for breathing air and must have regular access to air to survive.
Habitat and Behavior
Fiddler crabs are found in sand, mud and salt marshes near the high-tide line. Although males frequently fight each other for territory, they live in large colonies. They make their homes in slanted burrows that they dig out of the sand with their legs. The burrows can be up to three feet long. When high tide comes in fiddler crabs hide in their burrows with a bubble of air and plug up the entrance, only emerging when the tide recedes. They also spend the winter hidden in their burrows.
Feeding
Fiddler crabs travel in groups of thousands of individuals scouring the beach for food. They feed on decaying plants, algae and bacteria. Fiddler crabs feed by scooping up sand with their claws and passing it to specialized mouth parts called maxillipeds. The maxillipeds scrape food particles out of the sand and push it into the mouth. The crab then ejects round balls of sand. The male can't use his giant claw for gathering food. Since males can only feed with one claw they often need to feed for twice as long as the females.
Mating and Reproduction
During the summer female fiddler crabs are able to mate about every four weeks while males can mate every day. Males attract mates by standing near their burrows and waving their giant claws at the females as they walk by. Females show their interest by stopping to watch for a few moments. The male will then run back and forth several times between the female and his burrow until she joins him in the burrow or leaves. After mating is complete, the male leaves the area and finds another burrow while the female stays behind and spends the next two weeks inside the burrow incubating her eggs. At the end of the two weeks, the female leaves the burrow and releases her eggs into the ocean where the young will develop.