TIDAL CYCLE BUT NOT TO MALE OR FEMALE DENSITIES BY

Males of several species of fiddler crabs construct sand structures at the entrance to their burrows to which they attract females for mating. Although sand structures are able to attract females, males do not always construct structures, and there is a considerable variation in the frequency of structure construction per day. To determine what factors cause the variation in the frequency of structure construction, I conducted a field observation on the structure construction of Uca lactea and examined the effects of air and soil temperatures, tidal amplitude, male and female densities, and the interaction between male and female densities. The frequency of structure construction was related to tidal amplitude. This may be a male response to the changing levels of female receptivity associated with the tidal cycle. The frequency of structure construction was also correlated positively with air temperature. Although courtship investment is expected to be influenced by the number of mates and rivals, neither male nor female density were significantly correlated with the frequency of structure construction