The use of claw colour and pattern for species recognition in the fiddler crab Uca mjoebergi

In the fiddler crab Uca mjoebergi, males attract females to their burrows by waving their enlarged yellow claw. Colour is clearly involved in species recognition in U. mjoebergi, but the role of the species-specific colour pattern has not been investigated.

Here we show that U. mjoebergi females preferentially approach uniformaly yellow claws over bicoloured, yellow and white, claws. This is not due to a preference for a larger yellow signal, as they fail to discriminate between bicoloured claws differing in the proportion of yellow. Claw colour and pattern appear to be equally important in the recognition of conspecific males, as females do not distinguish between a uniformly coloured claw of the wrong colour and a claw containing yellow in the wrong pattern.

Experiments were conducted in October 2005, near the mangrove boardwalk in the East Point Reserve, Darwin, NT.