If You Give a Frog Testosterone, It Will Show You Its Foot

Some frogs trick their male competitors with a theatrical leg kick. A new study digs further into why the unusual gesture may have evolved.

The male Bornean rock frog cannot scream over the sound of a waterfall. Instead, he threatens other frogs with his feet. The frog intimidates his male competitors with a can-can-like gesture: kicking his leg up into the air, fully extending his splayed foot, and dragging it down toward the ground.

This foot-flagging display may not sound threatening to a human, but its effect has to do with a frog’s visual perception.

To a frog, the world contains two kinds of objects: things that are worms, and things that are not worms.