Detecting patterns between anthropogenic shell choice and predation, competition, sex or size in the hermit crab Pagurus granosimanus

Abstract

Marine debris has many impacts on intertidal ecosystems, and hermit crabs across various species and locations have been photographed using marine debris as shells. While hermit crab shell selectivity is a well-studied behavior, little is known about why hermit crabs are using anthropogenic shells. This paper tested for a relationship between bottle cap shell selection and four variables: competition, predation, sex, and size. Pagurus granosimanus hermit crabs were collected from three locations on San Juan Island, Washington and research was conducted at Friday Harbor Laboratories. Experiments simulated the presence of competition and/or predation and observed unshelled crabs as they selected among various gastropod shells and plastic bottle caps. The results indicated no significant relationships between shell preference and competition, predation, sex, and size. The paper makes suggestions for future research on both why hermit crabs are using marine debris and how this behavior may impact hermit crab ecology.