Vocal communication recorded in 53 animals we thought were silent

New recordings of sounds made by reptiles, amphibians and fish suggest that vocal communication has a common evolutionary origin in vertebrates

By Christa Lesté-Lasserre

Juvenile ornate or painted wood turtle (Rhinoclemmys pulcherrima), a species now known to be vocal

Jorgewich-Cohen et al.

Vocal communication is much more widespread in vertebrate animals than we thought.

Gabriel Jorgewich-Cohen at the University of Zurich, Switzerland, and his colleagues collected recordings from 53 species that were previously thought to be non-vocal, including the tuatara (Sphenodon punctatus), the Cayenne caecilian (Typhlonectes compressicauda), the South American lungfish (Lepidosiren paradoxa) and 50 species of turtles.

Rather than evolving in many animals independently, the research suggests that vocal communication arose in a common ancestor more than 400 million years ago.

Many vertebrates with lungs – a group known as choanate vertebrates – create sounds through structures in their throats as they push air up through the lungs. They use these sounds in social interactions like parental care, mate selection, territory marking and other behaviours that benefit from vocal communication.

However, researchers have overlooked at least 100 choanates in vocal communication studies, says Jorgewich-Cohen. That is because even though they could occasionally be heard making sounds, it was assumed that these noises were either created by accident or they were intended to defend themselves from other species – and hence that they couldn’t be considered true vocal communication.

In particular, people have often incorrectly assumed that turtles are non-vocal, says Jorgewich-Cohen. After participating in a field study on vocal communication in turtles, he was inspired to investigate further – starting with his own pet turtles. “I decided to record them, just to check it out,” he says. “I found several sounds there, and then we just kept going [with more species]. And suddenly, I had good sampling and I could understand a bigger picture.”

The 53 species the team studied had a varying range of acoustic capabilities, from chirps and clicks to more advanced, complex sounds of different tones. Many researchers agree that when animals use their respiratory tracts to create complex repertoires of different sounds or harmonic calls, they are communicating with each other, says Jorgewich-Cohen.

He also filmed with underwater cameras while recording sound to investigate what behaviours might be linked to the noises. The most obvious forms of communication were produced by males while courting females or during conflicts with other males.

By combining their findings with data collected previously on 1800 additional species of choanates, Jorgewich-Cohen and his colleagues determined that acoustic communication evolved in nose-breathing vertebrates about 407 million years ago. This means vocal communication is at least as old as the lobe-finned fish Eoactinistia foreyi, which is considered a possible last common ancestor of all choanate vertebrates.

In fact, vocal communication might be even more ancient than that, says Jorgewich-Cohen. Lungless fish produce vocal sounds as well, and it is possible that they evolved this trait and then passed it on to later generations that developed lungs. “It could be that one lineage of those fishes was the precursor of the type of sound that we make as [choanates],” he says. “So it could be actually that this lineage of sound production is older than what I found.”

Gerald Kuchling at the University of Western Australia says it is interesting that turtle vocalisations have been ignored for so long. “I am not surprised that all of them appear to vocalise,” he says. “I think it is significant that inserting this finding into a phylogeny [evolutionary tree] reveals this as an old, basic common trait of choanates generally.”

Journal reference: Nature Communications, DOI: 10.1038/s41467-022-33741-8

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