Variation in courtship rate in the fiddler crab Uca annulipes: Is it related to male attractiveness?

We investigated among-male variation in courtship waving in the fiddler crab Uca annulipes. Wave rate is positively correlated with both male carapace size and relative claw size (controlled for body size), and relative claw size is positively correlated with an index of body condition. An experimental reduction in the availability of food decreased male wave rate. These data suggest that some of the variation in wave rate among males is due to variation in male condition combined with energetic costs to waving (differential costs). However, we also found that the correlation between male size and wave rate decreased over the semilunar cycle. Later in the cycle, smaller males increase their wave rate relative to that of larger males. Previous work has shown that females are more likely to accept a smaller male as a mate later in the cycle. We suggest that smaller males invest disproportionately more in courtship later in the cycle because the potential benefits are greater due to their increased attractiveness to females (differential benefits). Alternative explanations for the observed temporal trend are also discussed.