Shell exchanges in the hermit crab Calcinus tibicen

Abstract

Shell exchange interactions of individuals of the hermit crab Calcinus tibicen were examined to see if these crabs behaved in a pattern which was similar to that observed in other species. Multiple regression analyses indicated that crab weight and shell internal volume were the best and sufficient estimators of crab and shell sizes. The model of exchange which best predicted the outcomes of naturally occurring interactions with the fewest parameters was the negotiations model (exchange should occur only if both participants gain in shell fit) using shell volume as the shell size parameter. Models which incorporated shell species considerations or both negotiations and aggressive elements increased the predictive powers, and overall the outcomes of 87% of the 202 shell exchange interactions of C. tibicen were predicted correctly.