FIDDLER CRABS – Why are some left-handed and some right-handed?



Sometimes known as “calling crabs” because during courtship, the male Fiddler Crab (Lower of the two crabs – other is a Female fiddler) wave their oversize claws high in the air and tap them on the ground in an effort to attract females. There is approx 100 species of these crabs worldwide that make up the genus ”Uca”.  As members of the family ”Ocypodae”, Fiddler Crabs are most closely related to the Ghost Crabs of the genus ”Ocypode”. This entire group is composed of small crabs – the largest being slightly over 50mm across.

Fiddler crabs are found along sea beaches, brackish intertidal mud flats, lagoons and swamps.  Like all crabs, they shed their shells as they grow. If they have lost legs or claws during their present growth cycle a new one will be present when they molt. When a large claw is lost (whichever side it’s on) a smaller version of itself regenerates, which grows over the next few molts. Newly molted crabs are very vulnerable because of their soft shells. They are reclusive and hide until the new shell hardens. They seem to eat throughout the low tide period. The male crabs smaller claw picks up a chunk of sediment from the ground and brings it to its mouth where its content is sifted through. The feeding habits of Fiddler Crabs play a vital role in the preservation or wetland environments.

Words and Photos by Graham Cumming

with an update from Judith S Weis, Professor Emerita, Rutgers University, New Jersey USA

Copyright 2018