Gabriel Jorgewich Cohen
In the animal kingdom, certain creatures are famous for the sounds they emit: birds and their songs, cats and their meows, frogs and their ribbits.
But some animals are more discreetly mysterious. Do turtles talk? What about other lesser known vertebrates such as tuataras, caecilians and lungfish?
The answer is yes, according to a new paper in Nature Communication presenting evidence that many species thought to be dumb actually vocalize – and the researchers recorded it on tape.
Gabriel Jorgewich Cohen, an evolutionary biologist working on his PhD at the University of Zurich, is the paper’s lead author.
He explains that this project started after he read about a turtle in the Amazon making sounds, and he started wondering about the little sounds his own pet turtles were making. He got in touch with a researcher from his old university in Brazil who had created a tool that was going to be crucial for research.
“He developed a type of hydrophone, which is pretty much a microphone that goes underwater,” says Jorgewich Cohen. “I took him home and started recording my own pets. And I heard them making a lot of noises.”
The project was launched. He traveled to eight or nine institutions in five countries, with the goal of registering animal species that were thought to be mostly mute. He recorded fifty species of turtles, as well as caecilians, tuataras (a reptile now only found in New Zealand) and lungfish (fish that can breathe air).
And it turned out, nothing of them were mute. “In fact, every animal I recorded was making sounds,” says Jorgewich Cohen.
He says the findings point to a common ancestor around 407 million years ago.
“It’s sometimes surprising how little we still know about things that aren’t necessarily rare but live alongside us,” says Neil Kelley, a paleontologist at Vanderbilt University.
Kelley says the paper’s conclusion, mapping these vocalizations on the evolutionary tree, makes sense. He notes that there are unique challenges to trying to study animal sounds over millions of years.
“It’s very difficult to trace this in the fossil record, because sounds obviously don’t fossilize and most vocal equipment is soft tissue-based,” he notes.
Gabriel Jorgewich Cohen
It is important to note that sound production and hearing are different things. Snakes, for example, are famous for their hissing sounds. But we don’t think they can hear themselves – or each other – whistle.
And a turtle making sounds doesn’t necessarily mean it’s communicating that way, says John Wiens, a professor of ecology and evolutionary biology at the University of Arizona.
“I think there is some confusion between sound production and acoustic communication,” he says of the newspaper.
Jorgewich Cohen says that although the research team is unsure of the meaning of all the sounds they collected, they used several strategies to identify the sounds used for communication, including the use of cameras to correlating sounds with behaviors that might demonstrate some sort of intent, and only including sounds that occur repeatedly and seem to correlate with social behavior.
Wiens says recording these sounds is an important step towards better understanding.
“If you’re not recording these sounds and reporting them, then there’s no reason for anyone to study acoustic communication in these things,” he says. “You don’t even know they make noises.”
The next step, he says, is to figure out what these animals might actually be saying.