How hermit crabs Pagurus bernhardus L. deal with obstructions in the apertures of shells

Establishes how crabs deal with obstacles, whether the behaviour is dependent upon the nature of the obstruction (none, sand, cement, gravel), and how the additional work required by the crab might influence the motivation of the animal to utilize that shell. The subjects were small specimens of Pagurus bernhardus inhabiting Littorina obtusata shells, collected at the low tide mark on a beach at Ballywalter, Co Down. -from Authors