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

Abstract

We investigated among-male variation in courtship waving in the fiddler crab Uca annulipa. 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 die 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 die cycle because die potential benefits are greater due to their increased attractiveness to females (differential benefits). Alternative explanations for die observed temporal trend are also discussed. Kty words: courtship, female choice, fiddler crabs, male choice, ornaments, sexual selection, Uca annulipes. [Behav Ecol 9:605—611 (1998)]