Hermit Crabs Line Up By Size to Exchange Shells

Anyone with an older brother or sister knows that clothes “shopping” often meant begrudgingly sifting through hand-me-downs rather than perusing the latest fashions at the mall. But for hermit crabs, the hand-me-down system isn't second-best, it's a matter of life and death. And as a new clip from the BBC show Life Story shows, the swapping process is remarkably orderly.