Fiddler Crab (Uca various)


Class: Malacostraca
Order: Decapoda
Family:    Ocypodidae
Size:    Length: 1 to 1.5 inches (2.5 to 3.5 cm)
Weight: Unknown
Diet: Algae and decaying plant and animal matter
Distribution: Pacific ocean, south Atlantic ocean and the Mediterranean
Young:  Hundreds of eggs per season
Animal Predators:  Fish, raccoons and water birds
IUCN Status: No special status
Terms: No special terms
Lifespan: Up to 3 years in captivity



·       There are approximately 100 species of fiddler crab found throughout the world.

·       Like all crabs, fiddlers are decapods—which means they have 10 legs.

·       Fiddler crabs change colour—during the day they are dark and at night they are pale.



These tiny animals are named fiddler crabs because of the enlarged claw found on the male. The claw, which can weigh up to half their total body weight, is vividly coloured, and the crab holds it in front of him, similar to how a musician holds a violin. If the enlarged claw breaks off, his other, smaller claw grows larger and a new small claw grows where the large claw was. Females have two smaller claws. Adult fiddler crabs moult once or twice a year, growing a new and larger shell. They have gills for breathing in the water as well as a lung enabling them to live on land. However, they cannot live only in water or only on land; they need both to survive.



There are many different fiddler crabs found along temperate and tropical seacoasts around the world, including three species found along the east coast of North America north of Florida—Marsh Fiddler Crab (Uca pugnax), Sand Fiddler Crab (Uca pugilator), and Red-Jointed Fiddler Crab (Uca minax). Both males and females dig deep burrows in the mud or sand of beaches or on the edge of a marsh. Burrows provide a place to escape from predators and to get out of the sun. They plug the hole of the burrows with mud to avoid being flooded out during high tide. 


Feeding Habits

Fiddler crabs eat in a puddle of water to separate the algae and other vegetation they eat from sand particles. Males are only able to eat with their smaller claws. 



Mating season takes place during the summer, and male fiddler crabs build mating burrows that they vigorously defend from other males. They try to entice females into entering these burrows by standing in front of the burrow and waving with their larger claw as the females return from foraging during low tide. The females look the males over, and if one seems to be interested in one of the males, he will rush to her and then rush back to his burrow, to let her know where it is. He does this several times, until she follows him to the opening of the burrow. When she approaches the opening, the male goes inside and drums against the side of the burrow. She feels the vibrations and if she is still impressed, she follows him inside. The female carries her eggs close to her abdomen. When they are ready to hatch, after two weeks of incubation, she releases them in water. They come out as larvae and do not resemble their parents at all. The babies go through five growth stages within one year. 



Although they live alone in their burrow, there are usually hundreds or thousands of other fiddler crabs in the area and they are outgoing with each other, although timid of other species. Fiddler crabs are poor swimmers and rarely enter the water. During the winter, they hibernate in their burrow, while during spring and summer, they only retreat to their burrow during high tide. When the tide goes out, they scurry out from their burrow and scramble to collect food. Fiddler crabs are non-violent with other species and although male fiddler crabs may wrestle together, they rarely suffer injuries; it is done mostly for show. 



Fiddler crabs are not a conservation concern. 



Fiddler Crab Wildlife Fact File, IM Pub, US