Shell dynamics and microhabitat selection by striped legged hermit crabs, Clibanarius vittatus (Bosc)

Hermit crabs respond to odors signaling potential shell availability by (1) withdrawing if they are in relatively large shells; (2) fleeing if the shells are ones they would occupy if given choices; (3) investigating if the shells occupied are relatively small. We used these behavioral responses as measures of shell fit to assess shell resources of Clibanarius vittatus (Bosc). From analysis of responses we conclude shell resources are dynamic. Behavioral tests suggest many crabs occupied relatively large shells in the spring and relatively small shells in the fall. Crabs in shells in which they would remain when presented with excess shells never comprised more than 30% of the population at any time of the year. Behavior of subpopulations of crabs from sand/mud and oyster reef habitats and crabs on land or in water at low tide was determined. In the fall, crabs whose behavior indicated they occupied relatively small shells for their size were found mainly in sand/mud habitats and remained in the water at low tide. Crabs whose behavior suggested shells they occupied that fit well were rare. The few that were found were found mainly in sand/mud habitats and were equally distributed on land and water. Crabs behaving as if shells were large for their size were found distributed evenly throughout oyster reef and sand/mud habitats and on both land and in water at low tide. Distributional results could not be explained by reduced mobility. Movement studies showed that even crabs in weighted shells should not be trapped by a receding tide. We postulate crab habitat choice is a behavioral adjustment that compensates for imperfect shell fit. © 1995.

Duke Scholars

Author Daniel Rittschof Marine Science and Conservation