Site fidelity and homing behaviour in the intertidal species Chiton granosus (Polyplacophora) (Frembly 1889)

Homing behaviour is frequently observed in marine intertidal invertebrate species. This behaviour may help species to deal with the environmental variability of the intertidal, providing shelter during low tides and areas to explore and search for food during high tides. The capacity of individuals to show fidelity behaviour should be an adaptive trait, due to the uncertainty that finding a new shelter in each tidal cycle implies. Chiton granosus is a common polyplacophora of the Southeastern Pacific rocky intertidal zone. During high tides, individuals move throughout the substratum in search of food; meanwhile, they are found within crevices in groups of variable sizes during low tides. According to previous works, this species shows some degree of fidelity to these shelters. Using field and laboratory experiments, we herein evaluate the factors determining the degree of site fidelity in C. granosus, taking into account the distance travelled from the shelter and food availability. Also, we evaluated the importance that chemical signs from the pedal mucus have in aiding C. granosus to return to its refuge. Field observations showed that C. granosus presents variable levels of site fidelity covering a maximum distance of 50 cm from its shelter. Laboratory results suggested that fidelity to shelters is related to the proximity of food sources. Chemical cues from the pedal mucus could be used to find the shelter after exploratory activities during high tides.