MULTIPLE MECHANISMS OF RESOURCE ACQUISITION IN HERMIT-CRABS - SCRUMS AND ODOR-INDUCED GRASPING (DECAPODA, DIOGENIDAE)

Two behavioral mechanisms shown by hermit crabs (brief grasps of shell s and serum formation) which increase their chances of obtaining new g astropod shells were examined. Individuals of Clibanarius vittatus whi ch smell odors from the snail Littorina irrorata show brief grasps of L. irrorata shells occupied by hermit crabs but long grasps of empty s hells. The brief grasp allows identification of the species of shell a nd whether or not it is occupied. Hermit crabs which are attracted to and closely attend a pair of crabs engaged in shell exchange behavior (scrummage formation) sometimes obtain a shell vacated by the initiati ng crab as it moves into the shell vacated by the non-initiating crab. These behaviors minimize the time spent by crabs on shells that are n ot available for easy occupation.