Hermit crabs are always trading up, seeking bigger and bigger shells as their bodies grow. And they've found an amazing way to help each other (while helping themselves) find what they're looking for.
When a hermit crab is on the lookout for a bigger home and sees a discarded shell, it will inspect it. If that new shell fits perfectly, the crab will claim it and carry on with its day. But if the shell is too big, it waits instead — "for anywhere between 15 minutes and eight hours," according to Scientific American.
Eventually, other crabs will wander over to check out the shell.
If it's not the right fit for any of them, they'll stick around too, and the whole group will begin to organize itself by size, creating a mass of crustaceans that manages to be equally adorable and horrifying. ("Crab Centipede: The Movie," anyone?)
Once a crab comes along that's the perfect size for the vacant shell, everybody springs into action. One by one, they leave their existing shells and hop into their new ones, in what scientists call a "simultaneous vacancy chain."
This video, from BBC Earth's "Life Story" shows the entire process in all its organized glory. Spoiler alert: Despite their orderliness, hermit crabs still have to deal with some sneaky line-cutters.