A hermit crab is a small ocean creature that protects its soft body by living inside empty seashells. Unlike regular crabs with hard shells covering their whole bodies, hermit crabs have tough front claws and legs but soft, vulnerable abdomens. They solve this problem by backing into abandoned snail shells and carrying their borrowed homes wherever they go.

As a hermit crab grows, it must find larger shells to move into. When hermit crabs discover empty shells, they may gather and line up by size, waiting to trade up to bigger homes in a kind of shell exchange. If you watch one closely, you might see it tap and inspect a new shell before quickly switching houses.

The “hermit” part of their name comes from how they live in their shells, like hermits who live alone away from others. Pet hermit crabs are popular because they're fascinating to watch and relatively easy to care for. In the wild, they scuttle along beaches and tide pools, playing an important role in ocean ecosystems by cleaning up dead plant and animal material.