Behavioral and ecological correlates of female mate searching in the fiddler crab Uca crenulata

Abstract

Investigating factors that influence which sex searches for a mate helps to identify how and why mating location and the degree of selectivity for mates change with ecological conditions. Several ecological factors that are thought to affect which sex searches — density, sediment size, and predation — were measured in two populations of the fiddler crab, Uca crenulata. At one of these populations, two additional factors, clutch size and larval release synchrony, also were measured because these factors may affect females' reliance on maledefended stationary resources. Females produced clutches that protruded beyond their abdomens and they released larvae synchronously at biweekly intervals throughout the breeding season. Density, sediment size, and predation levels varied between the two populations. Only females searched for mates at the high-density, predator-free, sandy site, while both sexes searched at the lowdensity site that contained more silt and predators. Females did not stop searching when density was lowered in experimental enclosures set in the sandier area. This suggests that density is less important in determining which sex searches when sediment grain and clutch size are both large.