Hermit crabs

The hermit crab is a favourite of rockpool enthusiasts. You can never tell if that old whelk or periwinkle shell is home to one of these crustaceans. A hermit crab appropriates shells to protect its soft twisted abdomen from predators. As the hermit crab grows, an overly snug shell is abandoned in favour of a larger abode.

One empty shell can trigger a property rush as crabs gather and simultaneously pass discarded shells down the housing chain to smaller individuals. There are more than 1,000 species of hermit crab. Despite the common name, they are more closely related to lobsters than true crabs. They are found in rockpools, throughout the shore and even in deep sea waters. Hermit crabs are widespread around the British coast.