Marine Wildlife Encyclopedia
Orange Fiddler Crab Uca vocans
Like its close relative the ghost crab, the male orange fiddler crab also exhibits ritualistic displays to deter rivals. Males are easily recognized because one of their claws is greatly enlarged. In a mature adult this claw makes up more than half the crab’s body weight and is used both to attract potential mates and to ward off rival males. Observing the distinctive “courtship wave” of fiddler crabs is helpful in identifying different species.
Orange fiddler crabs are active during the day. As well as digging a main burrow up to 12 in (30 cm) deep, they create a number of bolt holes into which they can retreat if danger threatens. At high tide, they seal themselves into their burrows with a small pocket of air. The presence of air is essential for their survival because fiddler crabs obtain oxygen from air, not water, despite having gills.
Each species of fiddler crab waves its claw in a slightly different way. If this ritual movement does not deter a rival male, then two crabs may “arm-wrestle” each other to resolve their dispute. The weaker individual usually retreats before any serious damage is done.