Land hermit crabs use odors of dead conspecifics to locate shells

A series of experiments at two tropical locations tested the ability of land hermit crabs Coenobita perlatus (H. Milne Edwards) and Coenobita compressas (H. Milne Edwards) to detect and respond to odors of dead conspecifics. An attraction array compared numbers of crabs attending hidden food odors and dead conspecific odors. Pit experiments tested crab shell-acquisition behaviors at different hidden odors. Bucket experiments confined crabs collected from various categories (feeding crabs, wandering crabs and crabs aggregated at dead conspecific odors) and tested behavioral responses to odors and an empty shell. Land hermit crab behavior at both sites was similar. Crabs were attracted to dead conspecific odors up to 10 times more than to food odors. Crabs attracted to dead conspecifics displayed significantly more shell-acquisition behaviors: touching other crab's shells in an exploratory manner and switching shells if an empty shell was available. In buckets, crabs from each category switched into shells. Results are compared to previous reports of similar shell-seeking behaviors by marine hermit crabs in response to dead conspecific odors. It is suggested that responding to dead conspecific odors for shell source location is an evolutionarily conserved behavior developed before hermit crabs became terrestrial.