Social context of shell acquisition in Coenobita clypeatus hermit crabs

Abstract

Vacancy chains involve unique patterns of resource acquisition behaviors that determine how reusable resources are distributed through animal populations. Shell vacancy chains have been described for several hermit crab species, both terrestrial and marine, but little is known about the ecological and behavioral dynamics of shell choice in social versus solitary contexts. Here, we present a novel conceptual framework that differentiates 2 types of shell vacancy chain in hermit crabs and discuss fundamentally distinct predictions concerning the behavioral and ecological costs and benefits associated with synchronous versus asynchronous vacancy chains. In laboratory studies of the terrestrial hermit crab Coenobita clypeatus, we found support for the prediction that social context alters shell acquisition behaviors. Field observations demonstrated that both synchronous and asynchronous vacancy chains are common and revealed previously undescribed waiting and piggybacking behaviors that appear to facilitate synchronous vacancy chains. Additionally, simulation results from an agent-based model showed that population density and waiting behaviors can both influence the likelihood of synchronous vacancy chains. Together, these results indicate that better understanding of hermit crab resource acquisition requires studying social behaviors, including vacancy chain formation.