Behavioural evidence for body colour signaling in the fiddler crab Uca perplexa (Brachyura: Ocypodidae)

In the reproductive season, mature females of the fiddler crab Uca perplexa leave their burrows and wander about their habitat for mating. To clarify whether the fiddler crabs respond to colour or luminosity, I examined the behavioural responses of the males to the wandering females before and after the females were painted white, red, black or blue. The behaviours of the males were categorized into three types: lateral-circular wave and lateral-straight wave for courting, and repelling. Before painting, almost all of the males courted the females. After painting, significantly fewer males courted the red-, black- and blue-painted females than courted the white-painted females. These results mean that the fiddler crabs can discriminate colours or luminosity. The role of body colour as a visual signal in crab society is discussed.