Some frogs emit ultrasonic screams humans can't hear because they're so high

If a frog screams in a forest and no one is around, does it make a sound?

Some frogs scream so high that humans can't hear it.

Lots of frogs around the world use a scream to scare off predators but scientists have found frogs in the Brazilian Atlantic Forest that can scream at an ultrasonic level.

Researchers saw small leaf litter frogs open their mouths and throw back their heads as if they were screaming but no sound came out.

While other animals like whales, dogs and bats use ultrasound, it's the first recorded case of "defensive ultrasound" being used in frogs.

The Brazillian leaf litter frog has a scream so high humans struggle to hear it

Why can't humans hear these frogs?

Sound is made up of vibrations, and the higher sound, the more frequent the vibration.

Humans can hear sounds that have a frequency of between 20Hz (hertz) to 20kHz (kilohertz).

The scientists recorded the frogs as they were screaming with a high-frequency audio recorder which showed they had a frequency range of 7kHz to 44kHz.

Anything above 20kHz is classed as ultrasound, which means these froggy-screams can be ultrasonic!

Scientists have found lots of frogs around the world that can scream

Why do these frogs scream?

The researchers think the leaf litter frogs do it in response to predators to scare them off.

"Some potential predators of amphibians, such as bats, rodents and small primates, are able to emit and hear sounds at this frequency, which humans can't," said one of the authors of the study, Ubiratã Ferreira Souza.

Ubiratã's theory is that the scream could be used as a distress call or it could be used to "scare as many predators as possible."

But they also suggest it could be to attract a mate or call other frogs to attack the predator.