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How do hermit crabs pick the right shell?

Taking over empty shells for protection is a neat trick. However, for hermit crabs, the quest for the perfect home is a lifelong preoccupation full of compromise. Swapping shells is a risky, yet necessary, procedure for a constantly growing crab, and finding a good fit is more of an art than an exact science. This hasn’t stopped researchers observing how the European hermit crab surveys a prospective shell. A crab will use its stalked compound eyes to gauge a shell’s size, weight and even colour, and it also has a good feel, using its legs and antennae, to estimate the shell’s volume, shape, condition and manoeuvrability, and whether it is already occupied. Gathering and processing all this informationGillian Burke