Tiny Frog’s Silent Ultrasonic Scream

The Brazilian Atlantic Rainforest resounds with the high-pitched ‘screams’ of a minuscule amphibian in distress, a sound previously unnoticed by human ears.

Researchers have, for the first time, captured recordings of South American frogs emitting calls at frequencies beyond human perception but potentially unsettling to animals equipped with suitable receptors.

Dominance of the Leaf Litter Frog in the Forest Amphibian Community

The leaf litter frog (Haddadus binotatus) dominates the forest’s amphibian population. Despite their prevalence, these frogs are diminutive, with even the largest females barely reaching a length of 64 millimeters (2.5 inches).

Unable to engage in physical combat when threatened, they resort to vocalizing, emitting an ultrasonic distress call as a defensive measure.

While it has been known that certain frogs vocalize to communicate distress, warnings, and alarms, previous studies hinting at their ability to produce ultrasounds have now been substantiated by this new research.

“Predators of amphibians, like bats, rodents, and small primates, can emit and detect sounds at these frequencies, which are beyond human hearing,” explains behavioral ecologist Ubiratã Ferreira Souza from the State University of Campina in Brazil.

Potential Functions of the Distress Call Frequency Range

“We hypothesize that the distress call may target some of these predators, or the wide frequency range might serve a generalist purpose, intended to deter as many potential threats as possible.”

This vocalization is part of a broader defensive display. The leaf litter frog arches its back, raises its front body, and opens its mouth wide, seemingly gearing up to unleash the piercing scream, which is eventually emitted as the frog partially closes its mouth.

While humans can typically perceive sounds up to around 20 kilohertz, the software employed by Souza and his team to capture the frog’s distress call detected frequencies ranging from seven to 44 kilohertz.

The researchers believe that this extensive frequency range, combined with the frog’s assertive posture, serves as a deterrent against a broad array of predators. Given that other frogs in different regions have demonstrated similar powerful vocalizations, this behavior might be more prevalent than previously thought.

Amphibian Diversity in Brazil and Potential Widespread Vocalizations

“With Brazil boasting the world’s highest amphibian diversity, featuring over 2,000 described species, it’s plausible that other frogs also produce sounds within these frequencies,” notes Mariana Retuci Pontes, an ecologist from the State University of Campina.

During a January 2023 visit to the Upper Ribeira State Tourism Park, Pontes observed comparable behavior in another frog species, although she couldn’t confirm the presence of an ultrasonic frequency band in her recorded video.

The researchers acknowledge that the precise mechanisms through which these calls deter predators remain uncertain. They speculate that the calls might either directly scare off predators or attract the attention of the predator’s natural adversaries.

“Could it be possible that the call aims to lure an owl, which would then target a snake approaching the frog as prey?” Souza proposes.

Read the original article on: Science Alert

Read more: The Flea Toad May be the Tiniest Vertebrate on Earth