Mate Choice in the Big-Clawed Snapping Shrimp, Alpheus Heterochaelis Say, 1818

Abstract In socially monogamous animals mate choice can be expected when mates vary in quality, degree of parental investment, or ability to defend an important resource. Mate choice was expected in the big-clawed snapping shrimp, Alpheus heterochaelis Say, 1818, as female size is positively correlated with fecundity. In addition, males and females share a shelter, which they defend from intruders, and therefore, resource holding potential could be an important component in mate choice. We tested the effect of body size and shelter ownership on mate choice and on competition in both sexes. As shelter occupancy and defence may have an influence on pair formation and mate choice, we also tested competitive success in obtaining preferred shelters as a variable in mate choice. We did not find evidence that males preferred larger females, but showed that females preferred and competed for larger males. Females paired more frequently with smaller males that occupied a shelter than with smaller males without a shelter. Males were, however, more successful in evicting smaller same-sex conspecifics from preferred shelters than females were. This could indicate that competition for shelter favours males with larger claws, and hence, body size, as these are better able to defend a shelter from other conspecifics. A female may therefore choose larger males, because she is dependent on both a male and a shelter for successful reproduction.