Fiddler Crab
Uca spp.
Description:
Fiddler crabs are small, semi-terrestrial crabs; male fiddlers have one claw that is much larger than the other, while
females have equal-sized claws. During the day the crabs are dark but at night they become pale. Although they
are capable of movement in all directions, crabs tend to move sideways. Three species are commonly found in
Florida; the Red-jointed fiddler, Marsh or mud fiddler and the Sand fiddler.
Habitat:
Fiddler crabs live near water on the mud or sand. Some species live on sandy beaches that are somewhat protected
from extreme wave action. Others live in muddy marshes and estuaries. Fiddler crabs are poor swimmers and rarely
enter the water during their adult lives. They dig 1/2-inch-wide burrows that go almost straight down into the mud
or sand. They provide crabs with shelter from the sun and predators, and give them a place to stay during high tide.
The burrows are filled with mud balls during high tide and have small pockets of air inside so the crabs can breathe.
All crabs have gills, which they must keep moist in order to breathe.
Food:
Fiddler crabs are omnivorous; some are scavengers and others predators. They eat algae and detritus (decaying
plant and animal matter). Fiddlers must feed almost constantly, as sand and mud contain little organic matter.
Females actually have an advantage when it comes to finding and eating food, because both their claws are small
and dexterous.
Offspring:
When a female crab lays eggs, she holds them to her belly until they are ready to hatch. This mass of eggs is known
as a "sponge." When the several thousand babies inside the sponge hatch into the water, they are extremely tiny and
look nothing like adult fiddler crabs.
Fun Facts:
• If an adult male loses its fiddler claw, the remaining claw grows to the same size as the lost claw; the claw
it regenerates becomes the smaller claw.
• The common name, “Fiddler Crab”, comes from the feeding of the males, where the movement of the small
claw from the ground to its mouth resembles the motion of a bow moving across a fiddle.
• In summer, fiddlers tend to breed about every two weeks. During this period the male fiddler digs,
maintains and defends a tidy cylindrical burrow. When looking for a mate, he stands near the edge of the
burrow, often alongside a string of other males and their (similarly well-maintained) burrows, while the
females, returning from foraging, walk past. The male waves his large fiddler claw until he attracts the
attention of an interested female, who then stares at him for a short period. The male resumes his clawwaving, and if the female remains receptive, the male runs toward her, then runs back to his burrow, and
repeats this motion several times until she either moves on or follows him to the burrow. The male then
partly enters the burrow and drums the edge with his claw. If the female decides to enter the burrow, the
male leads her to the terminal "room", returns to the opening to plug up the entrance with sand or mud, and
descends to the female again to mate.