Atlantic marsh fiddler crab
Common Name: Atlantic marsh fiddler crab
Latin Name: (Uca pugnax)
Size/weight: A small crab whose body (or carapace) is about 1 inch across. Males are slightly larger than females and have a blue spot on the top center.
Range: Cape Cod down to northern Florida. This is the most common species of fiddler crab on the U.S. East Coast.
Habitat: in the intertidal mud of salt marshes. The crabs dig burrows, which they use for resting, mating, safety and hibernating. (They are known to roll up a ball of mud to plug their burrow hole at high tide.)
Diet: They eat the mud too – well, they eat the tiny bits of fungus, algae, microbes, decaying plant & animal matter, and other organisms in the mud. What they don’t digest is deposited back as little mud balls.
Predators: Herons, gulls and other birds; raccoons; blue crabs; and other marsh predators.
Description: Olive-brown in color. Dark banded walking legs. Slender eye stalks. Fiddler crabs are easily identified by the males, which have one ridiculously large yellowish claw – an adaptation that developed to help them attract females. A bigger claw gets the girl. The large claw, called the chela, can be either the male’s left or right. Also, males have a blue spot on the top center of their carapace.
Note: Because all their digging helps to aerate the marsh, fiddler crabs are great for a marsh’s health.
Why are they called fiddler crabs? When a male feeds, the back-and-forth movement of its small claw (from the ground to its mouth) near its large claw resembles the motion of someone moving a bow across a fiddle.
Fiddler crabs are very skittish and retreat quickly to their marsh burrows. If you don’t want to go marsh-muckin’ in search of fiddler crabs, you can find them in The Maritime Aquarium's Salt Marsh Gallery.