Commonly found at the sandy edges of salt marshes, tidal flats and on protected beaches where it forms large aggregations. They live in burrows that have only one opening, and can be up to 2ft (60cm) deep. Sand fiddler crabs usually feed close to these burrows so that they can quickly retreat if they are disturbed using a “mud plug” to close the opening of their burrow during high tide. They also hibernate, remaining in their burrows until the water warms up.
- Got the name “fiddler” because when the male waves his big claw it looks like a person playing the violin, or fiddle.
- Known to live in large colonies.
- Form two kinds of pellets: one is formed during feeding when they separate the food from the sand/mud, rolling it into little balls; and the second larger pellet is formed when they dig their burrows.
- Considered good bait for fishing.
The sand fiddler crab mainly eats bacteria, algae and detritus parts of dead organisms).
Fiddler crabs have claws that differ between the sexes and are highly adapted for different uses. Female fiddlers have two small claws, both of which they use to feed. They feed by wildly shoveling food into their mouths with both claws. Male fiddlers have one major and one minor claw. The large claw is used for courtship, mating and territorial defense, and can account for up to 65% of its body weight. Fiddler crabs rarely engage in conflict because it can be detrimental to both crabs involved, but if a male does lose its major claw its minor claw will grow into a major claw and the lost claw will regenerate into a new minor claw. Males can only feed with one claw because the major claw is too awkward for feeding. They generally must spend twice the amount of time feeding that females do because they can only use the one claw. Both males and females use their claws to sort food (algae, bacteria, decomposing plants and detritus) out of sand and mud. They also use these multi-purpose claws to dig elaborate burrows where large aggregations of crabs live together just below the sand/mud of salt marshes or protected beaches.
Fiddler crabs are not used as food for humans but are a very important food source for estuarine animals such as clapper rails, other marsh birds, blue crabs and many other species. As with many other animals that depend on estuarine habitats, fiddler crabs are in growing danger of losing their habitat because of land use practices that change or destroy their homes. Even though sand fiddler crabs are presently considered common throughout North America, without proper preservation of habitat, these crabs could suffer severe population depletion.