If humans had heard the turtles earlier, we would have known that they send messages
A scientist has discovered that 53 sea creatures previously thought to be silent can actually communicate.
The creatures were sending messages all along, but humans had never thought to listen, suggests Gabriel Jorgewich-Cohen.
He used microphones to record the species, including turtles, communicating to him that they wanted to mate or hatch from the egg.
The findings claim to rewrite some of what we know about evolution.
They suggest that all nose-breathing vertebrates that use sound to communicate descended from a single ancestor 400 million years ago.
It is a strong claim in evolutionary biology that debates whether living things descend from a single ancestor or from multiple origins.
Jorgewich-Cohen, a doctoral student at the University of Zurich in Switzerland, began her work with the intuition that marine animals might communicate with sound.
He used sound and video equipment to record 53 species in captivity around the world, including at Chester Zoo in England.
The creatures included 50 turtles, a tuatara, a lungfish and a caecilian.
All these animals were thought to be dumb, but Mr. Jorgewich-Cohen suggests that they were not heard because their sounds were difficult to detect.
“We know when a bird is singing. You don’t need anyone to tell you what it is. But some of these animals are very quiet or make a sound every other day,” he told BBC News.
Jorgewich-Cohen also suggested that humans have a bias towards land-dwelling creatures and therefore ignore underwater species.
Videotaping the animals when they made noises allowed him to connect the sound with an associated behavior, to distinguish them from accidental sounds that send no message.
“Sea turtles will sing from inside their egg to synchronize hatching,” he explained.
“If they scream from inside, they all come out together and hopefully they don’t get eaten.”
Tuataras make noise to prevent animals from entering their territory
Turtles also make noises to signal they want to mate, he said, pointing to videos of turtle mating sounds that are popular on social media.
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Jorgewich-Cohen also recorded tuataras making sounds to protect their territory.
He then began to consider what the discovery revealed about the evolution of noise-making animals.
Fossils often don’t tell scientists enough about the animals that lived millions of years ago, so they compare the behavior of living animals.
Using a technique called phylogenetic analysis, Jorgevich-Cohen traced the relationship between animals that make noise.
The technique works by comparing the behaviors of a species and mapping them like a family tree. If, for example, a human and a chimpanzee share a behavior such as making noise, it suggests that the common ancestor also produced sound.
He concluded that all acoustic communication in vertebrates descended from a single ancestor 400 million years ago, which was the Devonian period when most species lived underwater.
This contrasts with recent work that traced communicative sound to several different species back 200 million years.
Caecilians, a group of limbless underwater amphibians, can ‘talk’, it turns out
Biologist Catherine Hobaiter, who was not part of the research, told BBC News that the recordings of these 53 species were a welcome addition to what we know about acoustic communication.
“Comparing species like chimpanzees and humans only sets us back a few million years,” he said.
“We need to see common features between much more distant relatives to push our understanding back hundreds of millions of years.”
The research is published in the scientific journal Nature Communications.