Sexual differences in feeding by the fiddler crab, Uca lactea (De Haan)

Abstract

Daily sand pellet production by the fiddler crab Uca lactea (De Haan, 1935) that lived in cages in the natural habitat was examined for five months in 1971. In 1972 and 1973 a study was done to determine the number of days per month that crabs are active. Females were less active in July and August because they were incubating broods underground. The average number of active days per year was 100.6 for males and 92.5 for females. Using their two chelipeds, females scooped 55-57% more frequently than did males, who have only one cheliped that is useful for sediment feeding. The length of dactyl and width of claw tip of the male cheliped are about 10% larger than those of the female cheliped. The total number of sand pellets produced in one year is estimated to be 34,967 in males and 38,675 in females. Pellets dry weights are 1,011 g in both males and females with the carapace width of 16.0 mm.