Male-Male Competition and Female Behavior as Determinants of Male Mating Success in the Semi-Terrestrial Hermit Crab Coenobita Compressus (H. Milne Edwards)

Abstract

The sexual behavior of the hermit crab Coenobita compressus was studied. The size, gastropod shell species, and sexual behavior of males measured in terms of successful or unsuccessful mating (assessed by spermatophore transfer) are compared, as well as the role of these variables in male-male encounters for the access to females. Since female receptivity (assessed as degree of egg development) could also influence male mating success, the relative number of receptive and unreceptive females that had or did not have spermatophores is used to evaluate whether unreceptive females were induced to mate. We assessed how frequently receptive and unreceptive females were present in the population. An experiment determined if males were able to grab females according to female sexual receptivity. The results show that: 1) behavior and type of gastropod shell in males is not related to mating success; 2) large males won against small males during contests for the access to females; 3) only some receptive females (actually, the less common in the population) received spermatophores even when males tried to mate with receptive and unreceptive females; and 4) female behavior determined the outcome of mating success. These results indicate that male size is important only during male-male competition but not during female choice. Our results also suggest an active role of female behavior in determining the mating outcome and that males are unable to force females to mate, unlike other species in which females, receptive or not, are unable to evade male sexual assaults.