Behavioral trade-off on shell exchange and exploration of the white spotwrist hermit crab Pagurus criniticornis (Crustacea, Anomura, Paguridae)

Abstract

The regulatory mechanisms of shell selection and occupation by hermit crabs can be determined by many factors such as competition, risk of predation, shell size, type and availability and also by physical damage. However, the relative importance among them has been scarcely studied. The aim of this study was to investigate the influence of predator, shell quality and size in shell exchanges and exploratory behaviors of Pagurus criniticornis. The experiments were carried out by placing a hermit crab with a naturally damaged shell in an arena with or without a caged predator (the narrowback mud crab, Panopeus americanus) and 10 empty shells. Concerning the male data and the shell exchange dependency on the factors of shell quality and predator presence, we suggest that individuals were sensitive to the predator presence when carrying a damaged shell. This data could represent a clear trade-off between the benefit of occupying a better shell and the imminent risk of predation. Considering that shells provide protection and that extremely damaged shells may increase the risk of predation, the exchange behavior is directly related to the increase in protection from predators, even if the exchange activity itself exposes the animal to a high predation risk for a short time.