Hermit crab house swap

Hermit crabs regularly upgrade their shells, but finding the right home requires great patience and cooperation with other house hunters

Life Story’s hermit crab has to wait at the end of a 'housing chain' created by a vacant sea shell being washed up on the shoreline.

Second-hand shells provide shelter for hermit crabs, giving their soft bodies extra protection from predators. But the crabs frequently need to find new homes as they grow bigger.

Even if an empty shell is unsuitable for a hermit crab's latest size requirements, they don’t carry on their house hunt elsewhere. Instead, they wait for other crabs to see the shell.

The Life Story crab was filmed on a small Caribbean island off the coast of Belize, where the supply of suitable shells is limited. 

As it waits beside an abandoned but oversized shell, more crabs soon show up. They take a look around the shell, but finding it to be far from their des res, begin inspecting the other crabs’ shells.

Soon a queue of house hunters forms in size order, all waiting for the “housing chain” to be completed by a bigger crab snapping up the new shell.

Finally when such a crab arrives the 'chain' sparks into life as the crabs vacate their old shells and climb into their new homes.

However, as Life Story’s crab finds out, hermit crabs can resort to underhand tactics, 'gazumping' the best shells.

As house moves often happen very quickly, unsuccessful house hunters have to take what’s left and hope they are nearby when the next chain begins.

Watch the hermit crab wait for its perfect home in episode three of Life Story at 21:00, Thursday 6th November, BBC One.