Competitive fighting for shells in the hermit crab,Clibanarius vittatus

The aggressive behavior of large Clibanarius vittatus against small C. vittatus was investigated. Large C. vittatus were more aggressive and showed fewer fear reactions in all conditions tested. The degree of dominance of large over small C. vittatus was much more marked and more predictable when the smaller crab occupied a Polinices rather than a Littorina shell and the large crab occupied a Littorina shell in both conditions. Evidence is given to suggest that C. vittatus reacts more to the shape than the size dimensions of a Polinices shell, and that small crabs occupying a Polinices shell are less active than other crabs occupying a Littorina shell.