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How Hermit Crabs Find Their Shells

a close up of an animal

Ever wonder how a hermit crab finds its perfect shell? Some shells are too big and some are too small and pretty soon this becomes a retelling of Goldilocks. But several different species, both terrestrial and marine hermit crabs, have developed their own system of finding one that’s “just right.” How? They’ve been known to form vacancy chains as a way to exchange shells between them.

It works like this. One crab finds a vacant shell, but alas, it’s too big for him. Instead of moving on he waits there. Soon, other hermit crabs arrive, they see that the vacant shell is too big for them as well, but they wait, and they all begin to form an orderly line ranging from the biggest among them to the smallest. Finally, when the right size hermit crab comes along he sees that the vacant shell is just what he needs: the perfect upgrade, room-wise, for him to continue to grow. He abandons his old shell, and all the hermit crabs waiting in line rapidly exchange theirs in sequence, so by the end of it, they all have a larger shell that is just right for them.

Hermit crabs are fascinating creatures and on our Mangrove Lagoon Cas Cay tours you get a chance to see them face to face and even participate in a hermit crab race!



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