Katherine Rundell, 6 February 2020
They are not, in fact, hermitical: they’re sociable, often climbing on top of one another to sleep in great piles, and their group behaviour is so intricately ordered that they make the politics of Renaissance courts look simplistic. When a crab comes across a new shell, it will climb into it and try it on for size. If the shell is of good quality but too big, it waits nearby for another crab to come and inspect it. If that crab also finds it too large, it joins the first crab, holding onto its claw until a queue develops – it can stretch to twenty crabs, arranged in order of size from smallest to largest, each holding onto the next: a hermit crab chorus line. When at last a crab arrives who can fit the vacant shell, the first crab in line claims the new crab’s former shell, and there is a flurry of crabs climbing into their neighbour’s home. The crab’s abdomen is soft and vulnerable to attack while exposed, so the whole process takes place with astonishing rapidity.