Tiny Crabs Gather to Do a Synchronized ‘Dance’ Every Year — And the Reason Why Is Surprisingly Sweet
The fiddler crabs can be seen performing their instinctual choreography through the summer
Male fiddler crabs perform a claw waving display on Japan’s Miwasaki coast each spring to attract mates and deter rivals
The synchronized movements help males stand out and are part of a species specific mating strategy observed worldwide
The annual phenomenon highlights nature’s intricate behaviors and draws attention to these tiny crabs’ unique courtship rituals
Every spring, along the coast of Japan, thousands of crabs throw a dance party, and they’ve been doing it for centuries.
According to News On Japan, on the Miwasaki coast in Shingu, Wakayama Prefecture, tiny male fiddler crabs have beg.un emerging from their burrows at low tide, rhythmically raising and lowering their claws in what looks strikingly like a choreographed routine.
A group of five fiddler crabs gathered on wet sand.
The crabs, whose sh3lls measure just about half an inch across, appear in ma.ssive numbers on the exposed tidal flats each year as temperatures climb, usually starting in May. According to experts, the display is expected to continue through the summer.
So what’s behind the adorable performance? It’s all about love and a little intimidation. The claw waving behavior is common among fiddler crabs and related species worldwide. Researchers believe the practice serves a dual purpose: attracting potential mates and warning rival males to back off, according to the Smithsonian National Museum of Natural History.
Males typically have one enlarged claw that they wave in elaborate, species specific patterns, which have been described as a biological calling card that females use to a.ssess a suitor’s strength and suitability.
Research has shown that the movements also create vibrations in the sand that signal their prowess to potential mates.
“It was things like bouncing on their legs, it was simultaneously crushing their claw and their body into the sand,” Beth Mortimer, an a.ssociate professor of biology at the University of Oxford who has researched European fiddler crab courting rituals, told NPR. “It was a lot more complex than we expected going in.”
Mortimer explained the four steps to the courting dance. First, the male crab will wave his claw in the air. Then, he’ll alternate waving his claw and dropping his body into the sand. He’ll continue to wave and drop his body, creating a more sustained “thumping” sound, until, if all that is successful, a female fiddler crab approaches and he starts drumming underground.
“Visually, they can’t be seen either by us or the females, but it does have a very, very strong seismic component,” Mortimer explained. “It’s ‘come and find me in my underground house, lad1es.'”
