Factors Influencing Shell Investigation in the Hermit Crab, Pagurus bernhardus


Ulster Trust for Nature Conservation, Barnett's Cottage, Barnett Demesne, Malone Road, Belfast BT9 5PB, Northern Ireland.


Laboratory experiments in which littoral specimens of Pagurus bernhardus were offered shells with blocked apertures showed that animals occupying poor quality shells approached and contacted new shells more quickly, spent longer investigating them, and spent a greater proportion of that time in active exploration of them than did animals in better shells. Animals spent less time investigating shells smaller than the optimal size than they did good quality shells, even though none of the shells could be occupied. Crabs spent less time investigating a new shell when a visible stimulus (a stone, a shell or another crab) was present. Shell assessment was thus influenced by the quality of the crab's own shell, the quality of the offered shell and the presence of other features in the animal's environment.