Wednesday, October 13, 2010

Hermit Crab Vacancy Chain

When I was single I rented a one-bedroom apartment. It was the perfect amount of space for a social hermit.

When I got married, more space was required and we moved into a two-bedroom apartment with two cats.

With a baby on the way, the space requirements have leaped considerably and we now have a spacious three-bedroom house. As space requirements changed I constantly looked around for new living quarters. But I never looked back until I thought about the Hermit Crab Vacancy Chain.

What sounds like branding nightmare for a chain of hotels, the Hermit Crab Vacancy Chain is an interesting study in recyclable resources. First of all, “Hermit” Crab is a misnomer. Although it’s usually a one crab, one shell scenario, Hermit Crabs (Pagurus sp.) are far more social then they are given credit for. It has less to do with loneliness and more to do with securing their next housing upgrade. As they outgrow their current living requirements they begin seeking new and improved digs. Unoccupied sea snail shells tend to be the preferred type as they can easily grasp the interior curvature of the shell.

Hermit Crabs will often gather around a new shell and line up for a fitting process in a game like musical shells. It’s known as a synchronous vacancy chain. If the new shell fits, the crab slips out of its old shell creating a vacancy for a smaller crab waiting nearby. Each subsequent smaller shell is tried on until each crab has a new upgrade.

The Hermit Crab I found on Bunche Beach in Fort Myers died of unknown causes. When resources are slim, fighting may occur and a crab can be left without a shell or even be killed. This one may have lived out its life in this Pear Whelk (Busycotypus spiratum). The ants will eat it and the tides may return the shell to the sea for a future occupant.

The housing market is such that I didn’t experience such harsh circumstances. In retrospect I think about the places I once lived and the people who slipped into them after my departure. Someday they’ll outgrow those places too and have an eye on a bigger home. For better or worse, shells abound here in south Florida.


  1. Funny you should post this today. I'm in charge of procuring two hermit crabs for Campbell's preschool class.

  2. I must say I'm glad that we don't have to carry our 2-bedroom bungalow around on our backs! The synchronous vacancy chain reminds me of hand-me-down clothes from my cousins - my sister and I would both try each item on and keep the ones that fit us best.