Hermit Crab Real Estate Market Controlled by Social Networking

hermit crab red shell photo

Image credit: jessica.diamond/Flickr

There are few things worse than moving. Packing everything in boxes, hauling across town—or to another city—and unpacking it again is exhausting. Even less enjoyable is the difficult process of finding a new house or apartment. It's hard to remember what the whole process was like without websites like Craigslist and Freecycle.

Hermit crabs, which have to upgrade into new shells as they grow, know a thing or two about the difficulties of frequent moves. It turns out they also understand how social networking can make it a lot easier.

hermit crab wall-e photo

Robots have Skynet, hermit crabs have the synchronous vacancy chain. Image credit: meddygarnet/Flickr

Few animals contend with the same challenge faced by hermit crabs: Because they live in abandoned snail shells, they must search continually for a new home as the grow throughout their lives. If they outgrow their old shell and cannot find a new one, the crabs are forced to wander "naked" until they do—their soft, vulnerable, bodies a tempting target for predators.

Hermit Crab Finds Use for Ocean Trash, Calls Broken Bottle Home

In spite of the demand, there simply aren't enough vacant snail shells available. Sara Lewis, professor of biology at Tufts University's School of Arts and Sciences, explains:

I've seen hermit crabs dragging around in bottle caps and even ballpoint pen tops. It's pathetic.

hermit crab blue shell photo

Image credit: jessica.diamond/Flickr

Dealing with the Housing Shortage

To cope with this shortage, the hermit crabs have developed an interesting organizational technique known as a "synchronous vacancy chain." When a crab in need of an upgrade happens upon a shell that is to big for it to occupy, it waits instead of moving on. Over time, a group forms around the large shell, lining up by size.

Once a crab arrives that is able to move into the largest, empty, home, a game of musical shells begins. The hermit crabs rapidly swap shells and, after only a few seconds, they have all found a new home.

Randi Rotjan, who conducted research on this process with Sara Lewis, commented:

They spend hours queuing up, and then the chain fires off in seconds, just like a line of dominoes.

And the behavior is not unique to hermit crabs. Lewis and Rotjan point out that many animals—including anemone-dwelling fish and tree-hole-seeking woodpeckers—utilize a synchronous vacancy chain to secure new homes.

hermit crab face photo

Image credit: Sreejith K/Flickr

From hermit crabs to fish, woodpeckers to humans, it's clear that social networking helps everyone find a better place to live.

Read more about animal homes:
Hermit Crab Finds Use for Ocean Trash, Calls Broken Bottle Home
Birdfeeders Found to Cause Evolution of New Species
Gimme Shelter: Climate Change is Making People Homeless

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