Variability of a dynamic visual signal: the fiddler crab claw-waving display.

Fiddler crabs use elaborate, species-specific claw-waving displays to communicate with rivals and mates. However, detailed comparative studies of fiddler crab signal structure and structural variations are lacking. This paper provides an analysis of the claw-waving displays of seven Australian species of fiddler crab, Uca mjoebergi, U. perplexa, U. polita, U. seismella, U. signata, U. elegans and U. vomeris. We used digital video to record and analyse the fine-scale spatiotemporal properties of these movement-based visual signals. We found that the structure and timing of the displays is species-specific, exhibiting inter-specific differences that follow phylogenetic relationships. The displays showed intra-specific variation according to individual identity, geographic location and fine-scale behavioural context. The observed differences and variations are discussed in the light of the evolutionary forces that may shape their design.