RELATIVE SIZE AND AGONISTIC BEHAVIOR IN THE FEMALE VELVET SWIMMING CRAB, NECORA PUBER (L) (BRACHYURA, PORTUNIDAE)

Female velvet swimming crabs (Necora puber) fight readily in the labor atory, with interactions being initiated equally often by the larger a nd smaller of the two opponents, but with the larger usually being vic torious. In 17 out of 65 interactions, however, a smaller crab won aga inst a larger one, and possible reasons for this are discussed. In two respects our results are surprising in the context of insights gained from games theory: firstly, the fights do not show a gradual pattern of escalation through display to overt physical violence; and secondly , fights do not become more costly in terms of either potential for in jury (intensity) or duration as the contestants became more evenly mat ched; indeed, as the contestants became more evenly matched, fight dur ation decreased.