A TEST FOR RESOURCE-DEFENSE MATING IN THE FIDDLER-CRAB UCA BEEBEI

Males of the fiddler crab Uca beebei defend, court from and attract females to burrows in intertidal mud flats. Females sequentially enter and leave several male burrows before they stay in one, mate and breed. This reproductive pattern is common among fiddler crabs and suggests that males may compete for females by competing for high-quality breeding sites and females may choose mates based on burrow quality. These ideas were tested for U. beebei by comparing structural features of (1) male and female burrows and (2) the male burrows females entered and left and those in which they mated. Male burrows had narrower openings and shafts than female burrows, but neither these nor 10 other burrow features differed between the male burrows females left and those in which they mated. Thus, there was no evidence of resource-defence mating in U. beebei. This pattern of mating behaviour may be rare in the genus because burrows suitable for breeding generally may be abundant and available to both sexes. Male fiddler crabs may compete for burrows due to their value for post-copulatory mate guarding and females may choose mates on the basis of courtship displays, not the quality of burrows for breeding.