Hermit Crab Vacancy Chains

Just learned about this interesting hermit crab behavior: You know how hermit crabs live in shells they find, right? (I.e., they can't grow their own shells and they don't generally kill other shelled animals so they can take the shell. They rely on finding an empty shell of the right size.) As it turns out, under the right conditions, some species form these surprisingly orderly queues when a crab finds a new, better shell. This is from a Behavioral Ecology article:

In hermit crabs, synchronous vacancy chains occur when several crabs queue up in decreasing size order. Once the largest crab moves into a vacant shell, a cascade of rapidly sequential shell-switches ensues, with vacancies trickling down to end at the least desirable shell.

It's a little funny because you see the same behavior in some families with computers or cell phones. You know, like Mom gets a new iPhone 5s, so the older kid gets her old iPhone 4 and the younger kid gets the older kid's HTC Evo, and the younger kid's crappy GoPhone gets sold on Amazon for $12.

We should all start referring to hand-me-downs as "synchronous vacancy chain resources."