Biologists from Ecuador capture the song of a toad considered mute for a century

A high-pitched sound in the woods caught the boy’s attention. Ecuadorian biologist Jorge Brito. He thought it was the cri-cri of a cricket, but he found a kind of toad with a prominent nose that since its discovery, a century ago, science believed to be mute.

“At first I thought it was some cricket that was out there vocalizingbut I noticed and became attentive”, recalls Brito, from the National Institute of Biodiversity (Inabio).

What he saw next was a toad that “although it did not inflate the uvular sac, a small flicker was visible” on its chin.

Already in the camp, this specimen of the species Rhinella festae made a sound again. It was not the common croaking of toads, but a very fine “ruuur-ruuur”. By chance, he found the evidence that collapsed the idea that this species could not sing due to its particular vocal anatomy.

In February the magazine Neotropical Biodiversity reported the finding. In his article, Brito and he also Ecuadorian biologist Diego Batallas described the sound of this species that inhabits the Cutucú and Cóndor Amazonian mountain ranges. The latter extends from Ecuador to Peru.

“This particular song of Rhinella festae is the first time it’s been recorded and it’s kind of surprising because, simply put, it shouldn’t be singing,” he tells the AFP battles.

This variety is known as the Santiago Valley toad. With brown and rough skin, it can measure between 45 and 68 millimeters. and is characterized by the head ending in a nasal prominence. The International Union for Conservation of Nature (IUCN) included it in its list of near threatened animals.

The dominant frequency of their song is in a range of 1.21 to 1.55 kilohertz, with one to two multi-pulsed notes, and an average duration of 0.72 seconds. “A very subtle sound and very difficult to hear in the field,” says Batallas, who before becoming a biologist was a chorister at a conservatory.

Everyone sings

Rhinella festae toads lack a sac and vocal slits. The first is a cartilage that inflates and acts as a speaker; the latter, a kind of valves that regulate the inlet and outlet of air.

Located under the chin, the vocal sac allows amphibians to amplify their song so that it can be heard more than 1 km away.

The fine thread of sound of the Rhinella festae would show that all species of toads sing.

“Very likely there are species that have gone unnoticed and that due to evolutionary processes that we do not know -which may be anti-predatory, which may be effects of the environment- do not need their sounds to be heard very far away,” says Batallas.

In the case of Rhinella festae, his song is advertising, as if it were a business card. In other species, croaking is associated with courtship and the defense of territory.

Ecuador, a small but megadiverse country, has 658 registered amphibian species. Of these, 623 correspond to toads and frogs and almost 60% are at risk or in critical danger of disappearing.

Only Brazil and Colombia have more amphibian species than Ecuador.

sound identity

In a laboratory in Quito, Brito has the stuffed specimen of the Rhinella festae toad that surprised science. He is still excited when he remembers the chance that led him to the discovery.

In 2016, he raised a inventory of the fauna that lives between the Upano and Abanico riversin the Amazonian province of Morona Santiago, on the border with Peru.

One night, he recounts, he entered the forest and caught the sound that he first mistook for that of a cricket. He contacted Batallas so that both, in the laboratory, will listen to the call of the toad.

“The first time I heard I said: ugh! this doesn’t sound like a toad, it’s like a kind of a little bird, a little trifle. It does not have the characteristics of an amphibian”, says Batallas.

With the certainty that it was a song never recorded by science, the researcher highlights the importance that, finally, the Rhinella festae have a sound identity like most species of toads.

This finding allows to implement less invasive methods of investigation, because the entry of people into fragile habitats is limited to avoid handling specimens. (I)