Intraspecific shell exchange in the hermit crab Clibanarius virescens (Krauss)

Abstract

Intraspecific shell exchange in the hermit crab Clibanarius virescens (Krauss) was studied by field and laboratory experiments. Shell exchange frequencies were determined in potentially competitive (only one individual of a pair would benefit from an exchange) and potentially mutualistic (both members benefit) situations. The frequency of competitive exchanges in laboratory experiments, which paired individuals occupying very poor quality shells and individuals occupying the shells in which they were collected, was very low (2%). Higher exchange frequencies were observed between individuals in poor quality shells and individuals in shells of their preferred size. Shell exchange frequencies were highest in mutualistic situations and situations in which all individuals occupied poor quality shells. Crabs which had been evicted from their shells by the experimenter prior to selecting new shells were evicted from the new shells in subsequent shell fight experiments significantly more often than crabs which had not been evicted. Field experiments resulted in exchange frequencies similar to those observed in the laboratory. The relevance of the present experiments to Maynard Smith and Parker's theory of asymmetric contests is discussed.