Brazilian researchers have discovered for the first time that some species of frogs use ultrasound for self-defense. This “frog cry” can stun predators while remaining undetectable to humans.
Ultrasound is actively used in the animal world for communication and echolocation. Creatures such as bats, dolphins, and whales utilize it. A new study demonstrates that some species of frogs may use ultrasound to signal distress and protect themselves.
Inaudible Cry
In a study published in the journal Acta Ethologica, scientists from the State University of Campinas in São Paulo (Brazil) conducted experiments on the leaf frogs Haddadus binotatus, which are endemic to the tropical forests of Brazil.
First, the researchers placed the animals in a “defense mode” by holding the frogs by their hind legs to simulate a predator attack.
The captured amphibians opened their mouths wide, threw back their heads, and emitted a cry. The frequency of their cry mainly exceeded 20 kHz (above the human hearing threshold) and reached up to 44 kHz. However, some sounds were in the range of 7 to 20 kHz.
According to the researchers, the ultrasonic cry of a trapped frog serves not only as a distress signal and a warning to its kin about danger but also as a means of protection. This is confirmed by the characteristic posture they adopt in response to threats from predators.
The scientists suggest that ultrasound may deter animals capable of perceiving it, such as bats, rodents, and small primates.
However, this is merely a hypothesis. According to another theory, the frog's cry may attract predators to its enemies. For example, as the scientists note, ultrasound could “attract an owl that will attack a snake about to eat a frog.”
