Abstract

The body size and residency status of male fiddler crabs, Uca vocans hesperiae, were examined as potential factors affecting fighting outcome. We observed 100 pairs of males naturally engaged in fighting behaviour and recorded fighting duration and the identity of the winners. Fighting pairs tend to be larger than average males in a population. Larger males tend to win fights regardless of residency status. Fighting duration was shorter when the size asymmetry between fighting pairs was greater. Residency status had no effect on fighting outcome.