In behavior never before recorded by scientists, male red-eyed tree frogs are shown shaking their rumps and entire bodies to show dominance. The shaking often precedes wrestling between the two males.

No, they’re not shivering. And no, they’re not getting shocked. These red-eyed tree frogs in Panama have been recorded shaking their behinds to send a message.

This shaking, known as tremulation, is a form of communication between male tree frogs.

The males are tremulating to establish which is the dominant male. They’re claiming territory for their ‘calling area’ where they spend the night calling for a female mate.

Sometimes, the shaking leads to wrestling among males… and maybe even more shaking, until the loser retreats.

Researcher Michael Caldwell of Boston University and his colleagues