Interpreting odours in hermit crabs: A comparative study

Odours of different sources can indicate to hermit crabs the availability of empty shells, crucial resources for the life cycle of almost all of them. Here, we compared Clibanarius erythropus and Pagurus bernhardus for the intensity of investigative behaviour exhibited towards an empty, well-fitting shell in the presence of (1) plain seawater as control and seawater conditioned by (2) dead and live snails, (3) dead and live conspecifics, (4) live predators, and (5) food. During 10 min of observation, we recorded latency (the time until the first contact with the shell), and the number and duration of shell investigation bouts. The two species behaved similarly when exposed to the odours of food, live snails, and predators, while a more intense shell investigation was induced by dead snail odour in C. erythropus and by dead or live conspecific odour in P. bernhardus. Further studies should investigate the influence of phylogeny and ecology on this interspecific difference.

Research highlights
► Odours of different sources can indicate to hermit crabs the availability of empty shells.
► We compared the hermit crabs Clibanarius erythropus and Pagurus bernhardus for the intensity of investigative behaviour exhibited towards an empty shell in the presence of several odours.
► Their responses to the odours indicating shell availability significantly differed, as a possible reflection of the diverse tactic they adopt to obtain shells.
►  The central role played by chemical stimuli for the recruitment of empty shells by hermit crabs is confirmed.
► The relative importance of phylogeny and ecology on such interspecific differences will be explored in other populations and species.