Some frogs scream at an ear-splitting volume for other animals but its frequency is inaudible to humans, scientists have discovered.

While out in the Amazonian jungle studying frogs, researchers in Brazil noticed something strange.

Small leaf litter frogs were arching their backs, throwing back their heads and opening their mouths wide.

They looked like they were screaming but the scientists could hear nothing.

When they recorded the frogs using high-frequency audio recorders, the scientists captured the first documented case of “defensive ultrasound” being used by amphibians.