The European fiddler crab (Afruca tangeri) lives along the Atlantic coast, from Portugal in southwestern Europe to Angola in western Africa. Male crabs have one small claw and one big claw that they use in their dances to attract a mate.

The male European fiddler crab attracts his mate by performing a courtship dance. New research says that dance isn't just notable for its visuals — it's notable for its vibrations, too.

During courtship, the male crab waves his major claw up and down, drumming on the sand until females approach. This works even in the dark. So, researchers believe that the way the crabs' drumming moves through the sand is key to the process.

Using geophones, which sense and record the crabs' seismic vibrations, researchers from the University of Oxford were able to listen in on these percussive love songs. They realized that the vibrations were created by a number of different behaviors, not just the claw drumming.

"It was things like bouncing on their legs, it was simultaneously crushing their claw and their body into the sand," says Beth Mortimer, one of the study authors and an associate professor of biology at the University of Oxford. "It was a lot more complex than we expected going in."

Altogether, researchers observed four different stages of the courtship dance, with each stage escalating the amount of vibrational output generated.

First, the male crab waves his claw in the air. Second, he alternates waving and dropping his body into the sand. Then, he simultaneously waves and drops his body, creating a more sustained thumping noise. And finally, if all that is successful and the female fiddler crab approaches, he begins 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 says. "It's 'come and find me in my underground house, ladies.'"

Interested in more seismic vibration communication? Send us an email at [email protected].

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This episode was produced by Hannah Chinn and Kathryn Fink. It was edited by Patrick Jarenwattananon. Tyler Jones checked the facts.