As a hermit crab grows, its shell becomes a tighter fit so eventually the crabs need to move into a bigger one, leading to this amazing exchange 🦀🐚

Without shells, the crabs will bake under the sun’s punishing rays, if they aren’t eaten first. So, the hermit crabs form a conga line ordered from largest to smallest crab. As the largest crab enters its new home, the next crab in line takes the vacated shell, leaving an open shell for the crab behind him.

The shell swapping continues down the line until everyone has upgraded. This chain reaction is called a “vacancy chain,” and it’s an ingenious way for the creatures to survive while sharing limited resources