Recordings show some ‘mute’ animals communicate vocally: study

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Paris (AFP)- According to a study published on Tuesday, more than 50 animal species previously thought to be mute communicate vocally, suggesting the trait may have evolved from a common ancestor more than 400 million years ago.

The study’s lead author, evolutionary biologist Gabriel Jorgewich-Cohen, told AFP he first came up with the idea of ​​recording seemingly mute species while researching the turtles in the Amazon rainforest of Brazil.

“When I got home, I decided to start registering my own pets,” Jorgewich-Cohen said. This included Homer, a turtle he had had since childhood.

Much to his excitement, he discovered that Homer and his other pet turtles were making vocal sounds.

So he started recording other species of turtles, sometimes using a hydrophone, a microphone to record underwater.

“Every species I recorded made sounds,” said Jorgewich-Cohen, a researcher at the University of Zurich in Switzerland.

“Then we started wondering how many other animals normally considered dumb produce sounds.”

Along with more than 50 species of turtles, the study published in the journal Nature Communications also included recordings of three “very strange animals” thought to be mute, he said.

They include a type of lungfish, which has gills as well as lungs that allow it to survive on land, and a species of caecilian – a group of amphibians resembling a cross between a snake and a worm.

The research team also recorded a rare type of reptile found only in New Zealand called a tuatara, the only surviving member of an order called Rhynchocephalia that once covered the world.

All animals made vocal sounds such as clicks and chirps or tonal noises, although they were not very loud or only made them a few times a day.

Common vocal ancestor

The research team combined their findings with data on the evolutionary history of acoustic communication for another 1,800 species.

They then used an analysis called “ancestral state reconstruction”, which calculates the probability of a shared link over time.

It was previously thought that tetrapods – the four-limbed animals – and lungfish developed vocal communication separately.

“But now we’re showing the opposite,” Jorgewich-Cohen said. “They come from the same place”.

“What we found was that the common ancestor of this group was already making sounds and was intentionally communicating using those sounds,” Jorgewich-Cohen said.

The common ancestor lived at least 407 million years ago during the Paleozoic era, according to the study.

John Wiens, a professor of evolutionary biology at the University of Arizona in the United States, who was not involved in the research, said the suggestion that “acoustic communication arose in the common ancestor of fish- lung and tetrapods is interesting and surprising”.

Wiens, who published a 2020 paper titled “Origins of Acoustic Communication in Vertebrates,” welcomed the new data for additional species.

But he suggested the study might not “necessarily distinguish between animals making sounds and actual acoustic communication”.

Jorgewich-Cohen said the researchers had indeed set out to identify sound animals specially designed to communicate, comparing video and audio recordings to find matches for a particular behavior.

They also recorded the animals in different groups “so that we can tell if there are sounds that are only produced in specific situations,” he said.

He acknowledged that some species were difficult to study because they do not vocalize frequently and “tend to be shy”, adding that further research was needed.

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