Some amphibians emit ultrasound to defend themselves from predators. It is a distress call of deafening intensity for many animals, but inaudible for humans. Yes, frogs can shout for help.
This is documented by a new study published in the journal Acta Ethologica. He recorded the use of ultrasound by amphibians for the first time in South America.
audio software
«It happens with some potential predators of amphibians, such as bats, rodents and small primates. They are capable of emitting and hearing sounds at this frequency, something that humans cannot. One of our hypotheses is that the distress call is directed to some of them. It could also be the case that the wide frequency band is generalist. That is, it should scare as many predators as possible,” said Ubiratã Ferreira Souza. He is a researcher at the Institute of Biology of the State University of Campinas (IB-Unicamp), in Brazil.
Another hypothesis is that the cry is intended to attract another animal to attack the predator that threatens the amphibian. In this case, the leaf litter frog (Haddadus binotatus). It is an endemic species of the Brazilian Atlantic Forest, reports FAPESP.
Investigators recorded the distress call on two occasions. They analyzed the sound using special software. They found that it had a frequency range of 7 kilohertz (kHz) to 44 kHz. Humans cannot hear frequencies above 20 kHz, which are classified as ultrasound.
Other frogs
While emitting its distress call, this frog performs a series of movements typical of defense against predators. He lifts his forehead from his body, opens his mouth wide and throws his head back. Then he partially closes his mouth and emits a call. It ranges from a frequency band audible to humans (7 kHZ-20 kHz) to an inaudible ultrasound band (20 kHz-44 kHz). This way the frogs can shout for help.
«The diversity of amphibians in Brazil is the greatest in the world, with more than 2,000 described species. “It would not be surprising to find that other frogs also make sounds at these frequencies.” This was commented by Mariana Retuci Pontes, co-author of the article and doctoral candidate at IB-UNICAMP.
