The Fiddler Crab Dance: a Sexual Rock, Paper, Scissors

"Hey, I'm a synchronized dancer," has never been the best of pick-up lines, and now we know why. A recent study of fiddler crabs has revealed that their characteristic synchronized mating dances to attract a female are all about being off-beat, where the crab that dances most unlike the others is twice as likely to get the girl.

This is a startling revelation for experts, who have long thought that the impressive synchronicity of these displays was some strange form of crustacean camaraderie, in which males band together to present themselves equally and share the love.

However, in terms of sexual selection and evolution, that just didn't make any sense. Now, a study recently published in the journal Animal Behavior suggests that the dances may actually be a nearly ritualistic game of "rock, paper, scissors" to get the girl.

So what exactly does that mean? Fiddler crabs are best known for boasting one massive claw that is nearly half the creature's entire bodyweight.

When a lady crab comes along, male fiddlers will raise their collosal claw, showing it off as they dance. However, because they all raise and wave their claw at the first sign of a female, groups of males look stunningly synchronized - a flash mob of crabby claws.

In a series of lab experiments, researchers took several female fiddler crabs from the wild and exposed them to a room of robotic male decoys. These "males" were programmed to wave their claws in different ways - either synchronized, off-beat, or in counter to the rhythm of the "dance."

Without fail, the females were always drawn to the black sheep of the pack - the most unsynchronized claw waver.

Researcher Luke Holman explained to New Scientist that he suspects the synchronicity of the "dance" is just a symptom of strategy limitations, much like if 100 people play "rock, paper, scissors" at the same time, it will look like a lot are picking the same choice.

"It's a really chaotic environment they live in and maybe they are just trying to follow a few basic rules that end up backfiring," Holman said. "In a world where everyone is trying to be different, they all end up being exactly the same."

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