Secret communication of sea animals discovered

By Georgina Rannard, Oct. 26: A scientist has found 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 to them, Gabriel Jorgewich-Cohen suggests.

He used microphones to record the species, including turtles, communicating 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 vertebrates that breathe through their noses and 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 descended from a single ancestor or from multiple origins.

Jorgewich-Cohen, a PhD student at the University of Zurich, Switzerland began his work with a hunch 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.

It had been thought that all these animals were mute but Jorgewich-Cohen suggests they went unheard because their sounds were hard to detect.

"We know when a bird sings. You don't need anyone to tell you what it is. But some of these animals are very quiet or make a sound every two days," he told BBC News.

Jorgewich-Cohen also suggested that humans have a bias towards creatures that live on land and so they ignored species underwater.

Video records of the animals when they made noise allowed him to connect sound with an associated behaviour - to distinguish from accidental sounds that don't send a message.

"Sea turtles will sing from within their egg to synchronise hatching," he explained.

"If they call from inside, they all come out together and hopefully avoid being eaten."

Turtles also make noises to indicate they want to mate, he said, pointing to videos of turtle mating sounds that are popular on social media.

Jorgewich-Cohen also recorded tuataras making sounds to guard their territory.

He then began to consider what the discovery revealed about the evolution of noise-making animals.

Fossils often do not tell scientists enough about animals that lived millions of years ago so instead they compare the behaviour of living animals.

Using a technique called phylogenetic analysis, Jorgevich-Cohen traced back the relationship between noise-making animals.

The technique works by comparing the behaviours of a species and mapping them like a family tree. If, for example, a human and chimpanzee share behaviour like making noise it suggests that the ancestor in common 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.

That contrasts with recent work that traced the communicative sound to several different species 200 million years ago.

Biologist Catherine Hobaiter, who was not part of the research, told BBC News that recordings of these 53 species were a welcome addition to what we know about acoustic communication.

"Comparing species like chimpanzees and humans only gets us back a few million years," she said.

"We need to see common features across much more distant relatives to push our understanding back into hundreds of millions of years."

The research is published in the scientific journal Nature Communications.