ORCID

Abstract

Plastic pollution is one of the main human-induced rapid environmental changes threatening marine organisms. Terrestrial hermit crabs, which inhabit coastal areas where litter accumulates, are increasingly documented using plastic debris as shells, and a recent study hypothesized that this shift may be an adaptive response. They suggested that ‘plastic shells’ may reduce transport costs, provide camouflage in a polluted environment, and may even be favoured by sexual selection. Our study is the first to quantify plastic shell use in a population, to examine shell preference and to test the hypothesis that plastic shells optimize the ratio of weight to volume. We investigated the prevalence of plastic shell use by Coenobita compressus at Playa Nancite, Costa Rica. We conducted field surveys to assess shell use among hermit crabs, evaluated the environmental availability of natural and plastic shells, and performed a choice trial experiment to determine their shell preference. Of the 714 crabs collected, all were found in natural shells, despite the shoreline survey revealing a far greater abundance of available artificial shells, primarily plastic. Choice trials showed a strong preference for natural shells, with crabs only occasionally entering, and never retaining, plastic shells. Despite the widespread availability of plastic debris at Playa Nancite, hermit crabs strongly prefer natural shells, suggesting limited current impacts on this population's shell selection behaviour and evolution. However, the pervasive presence of plastic on beaches necessitates urgent measures to mitigate its environmental impact. Furthermore, research across different species and locations is essential to understand the broader implications of marine debris on hermit crabs.

Publication Date

2025-11-01

Publication Title

Animal Behaviour

Volume

229

ISSN

0003-3472

Acceptance Date

2025-07-14

Deposit Date

2025-10-31

Funding

We thank Anna Jung, Jakob Goulding, Joseph Jayasekera and Phoebe Blizzard for help with the data collection. Our stay at the Nancite research station was made both possible and far more enjoyable by Pablo Aguilar and Wilbert Villachica. The fieldwork in Costa Rica for this work was made possible by support from the School of Biological and Marine Sciences, University of Plymouth.

Keywords

Coenobita compressus, HIREC, human-induced rapid environmental change, plastic pollution, shell selection

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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