Habituation to disturbance in the fiddler crab (Uca annulipes) in its natural environment

Crabs of both sexes and of various sizes were subjected to a standardized test of ten consecutive disturbances in their natural habitat. Males and females reacted alike: 53 per cent became fully habituated within less than ten disturbances, and a further 12 per cent showed slower habituation. The remainder of the test individuals showed various other patterns of reactions. Reaction pattern and efficiency of habituation are size- (or age-) dependent, and they are modifiable by social interaction and by tide-determined activity phases. The structure and species composition (with regard to ocipodid crabs only) of the Uca habitat is considered briefly, and some observations on display and ‘rapping’ or drumming behaviour are reported.