Social networking helps hermit crabs locate better homes

Washington, April 27 (ANI): Hermit crabs locate new and improved housing using previously unknown social networking skills, according to a new study.

Biologists at Tufts University's School of Arts and Sciences and the New England Aquarium found that hermit crabs often find the best new shells when they gather together.

Hermit crabs have an unusual lifestyle because they require empty snail shells for shelter. They need to regularly seek new shells as they grow bigger throughout their lives.

"Hermit crabs are really picky about real estate because they're constantly getting thrown back into the housing market," said Randi Rotjan, leader of the research team and a co-author with Sara Lewis, professor of biology at Tufts University's School of Arts and Sciences.

Often there aren't enough suitable shells to go around and some hermit crabs have to go naked. The soft, exposed abdomen of these homeless crabs makes them more vulnerable to predators.

So, how do hermit crabs win this life-or-death shell game? One previously identified strategy that apparently helps each hermit crab find the very best shell is joining a lively group activity known as a synchronous vacancy chain.

When a new shell becomes available, crabs gather around it and queue up in a line from largest to smallest. Once the largest crab moves into the vacant shell, each crab in the queue swiftly switches into the newly vacated shell right in front of them.

As a result, a single vacant shell kicks off an entire chain of shell vacancies that ultimately leads to many crabs getting new, and generally improved, housing.

By seeding vacant shells into field populations and staying up all night to see what happened, the scientists discovered some previously unknown hermit crab behaviours.

When a hermit crab discovers an empty but oversized shell, it waits nearby rather than simply walking away. Once a small group gathers, crabs begin piggybacking by holding onto the shell of a larger crab and riding along.

Such waiting and piggybacking behaviours seem to increase the chances that a synchronous vacancy chain will happen.

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

Computer models populated with virtual hermit crabs and shells confirmed that synchronous vacancy chains depend not only on crab density, but also on how long crabs are programmed to wait near an unsuitable shell.

The study has been published in the May/June 2010 issue of the journal Behavioural Ecology. (ANI)