Hermit Crabs Form Orderly Lines to Upgrade to Bigger Shells, Giving Their Old Shells to a Crab in Need

A fascinating clip narrated by David Attenborough from the BBC nature show Life Story features a group of hermit crabs patiently forming an orderly line by their size when a new and larger shell washes up on shore. As the largest hermit crab leaves its shell to claim the new home, and the second-largest takes that now-vacant shell, and so on down the line until each crab has moved into a slightly larger shell.