Tiny frogs make ultrasonic sounds that exceed human hearing

To survive against stronger enemies, leaf frogs emit ultrasonic calls - sounds with frequencies exceeding the maximum frequency audible to the human ear .

Leaf frog - (Photo: National Geographic).

The leaf frog (Haddadus binotatus) is the most common frog species in the forest frog community in South America. Although there are many of them, they are very small, the largest being less than 64mm long.

When faced and unable to fight against the enemy, their defense strategy is to emit ultrasonic cries.

Recently, for the first time, researchers recorded the sounds of this frog species in Brazil. Although humans cannot hear it, this is a very unpleasant sound for predators such as bats, rodents and small primates.

This cry is part of a whole chain of defensive behavior of leaf frogs: they arch their back, while raising the front part of their body, their mouth opens wide as if preparing to "scream".

Illustration of the screaming behavior of a leaf frog.

The frequency of their calls, according to the research team, ranges from 7 to 44 kilohertz. Meanwhile, humans can only hear sounds of about 20 kilohertz or less.

Researchers believe that this wide frequency, along with the frog's intimidating posture, is intended to deter predators from attacking it.

"Since Brazil's amphibian diversity is the highest in the world, with more than 2,000 described species, it would not be surprising if other frog species also emit sounds at these frequencies ," says the ecologist said Mariana Retuci Pontes of Campina State University.

This research is published in the journal Acta ethologica .