If you’ve noticed a lot of traffic in the City of Pittsburgh and a few street closures in Oakland here’s why: This week is Move-In Day at every university in town — six of them.

Move-In Day is our annual human effort at something that hermit crabs do all the time. Because they outgrow their shells hermit crabs are frequently in the housing market. When lots of them need a new shell they get organized and all move-in at once. It’s called a synchronous vacancy chain and takes only a few minutes once it starts to roll.

Click the link to read more about Hermit Crab Move-In Day. It’s fascinating!

(photo from Wikimedia Commons; click on the caption to see the original)