Hermit crabs around the world resort to plastic trash to use as shells

Plastic shells have become a trend for hermit crabs all over the world. In a new study, scientists looked at how often hermit crabs use plastic and other man-made materials as shells, concluding that it is likely a universal problem in many different species.

Researchers at the University of Warsaw in Poland analyzed nearly 29,000 photos of hermit crabs uploaded to online platforms such as iNaturalist by wildlife enthusiasts.

They identified 386 crabs that chose artificial shells as their homes. The most common man-made material was plastic caps, like the ones you find on soda bottles, which account for up to 85 percent of artificial shells.

Overall, they estimate that the problem affects at least 10 of the 16 species of terrestrial hermit crabs found in tropical regions of the planet.

“When I first saw these images, I felt they were heartbreaking,” said Professor Marta Sulkin, study author from the Institute of Evolutionary Biology at the University of Warsaw. BBC Radio 4.

Examples of plastic-shelled hermit crabs used in the study.

Image credit: Sean Miller via Z. Jagiello et al., Total Ecology, 2024 (CC by 4.0 bond)

“At the same time, I think we really need to understand the fact that we live in a different era and animals benefit from what is available to them,” she added.

Hermit crabs have a soft abdomen with an exoskeleton that needs protection. To save on the energy-intensive process of growing their shells, they will simply snatch up discarded shells left behind by dead crustaceans. However, as the world's oceans become increasingly polluted with plastic, it seems that many hermit crabs are increasingly inclined to use garbage as their shelter.

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The new study investigated why hermit crabs abandon their typical natural shells in favor of artificial alternatives, concluding that it likely depends on a few different things.

Sexual selection is a possible factor because females may be attracted to the novelty of the plastic shell. Plastic is also generally lighter than chitin wraps, making it a more practical option. In addition, hermit crabs may choose plastic shells because they help them camouflage in polluted environments.

It is not clear whether plastic shells affect hermit crab health or are a benign consequence of living in the Anthropocene. In a follow-up study, the team hopes to reveal whether this new behavior affects hermit crab development.

“These analyzes will deepen our understanding of the consequences of plastic pollution on marine ecosystems, as well as the evolution of species in the context of new evolutionary pressures associated with the Anthropocene,” the researcher said in the journal. statement.

Hermit crabs are not alone in their plastic plight. Recently, scientists have documented the myriad ways in which the natural world is changing due to the increasing presence of plastic, from turtle stomachs filled with synthetic nets to ants tangled in synthetic fibers.

In one particularly striking example, geologists recently discovered “plastic rocks” on a remote volcanic island off the Brazilian coast.

The new study is published in the journal Holistic ecology.

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