VIDEO PLAYBACK EXPERIMENTS TESTING THE FUNCTION OF CLAW WAVING IN THE SAND FIDDLER CRAB

Abstract

Like many territory advertisement signals, the claw waving display of fiddler crabs (genus Uca) is commonly thought to have the dual function of simultaneously repelling males and attracting females. I have found, however, that male sand fiddler crabs (U. pugilator) wave significantly more in the presence of females than males, suggesting that their waves are primarily directed to females. Here I use laboratory video playback experiments to ask whether male and female U. pugilator are both responsive to the display. Males and females were presented with video of an example of either a waving or a feeding male conspecific, or no video, and their behavior was measured in seven behavioral categories that were then collapsed into three principal components. Analysis of variance of females' principal component scores revealed significant differences in their behavior in the presence of waving male video compared with feeding male video or no video, demonstrating that females attend to the display. Male behavior, however, was not significantly different between the three treatments, which is inconsistent with the hypothesis that claw waving serves to repel or threaten other males. These results, together with my recent work on male signaling behavior, suggests that the claw waving display of U. pugilator is a signal primarily directed to females and attended to by females, and thus is not an example of a dual function signal.