Vertebrates May Have Used Vocal Communication More Than 100 Million Years Earlier Than We Thought

Most people don't think of turtles as being very vocal. The research published today in Nature Communications shows that at least 50 turtle species vocalize. The evolutionary history of the species was studied in detail. Researchers were able to trace vocalizations back to an ancestors that lived over 400 million years ago.

Most of the species were considered to be silent prior to the study. The sounds that turtles are making have the same evolutionary origin as our own vocal communication.

Animals can communicate in a variety of ways. Most of the time, acoustic signals are the most widely used means of communication. A rattlesnake's rattle, a rabbit's thump, or a cricket's chirp are examples of non-vocally produced sounds that can be used in acoustic communication.

Scientists are interested in vocalizations because of their importance. Researchers trying to understand the evolutionary origins of vocalizations have to use data from current species because sound doesn't stay in the fossil record.

Scientists estimated that acoustic communication came about 100 million to 200 million years ago due to nocturnal activity. According to the 2020 paper, this form of communication emerged repeatedly and independently in most major vocalizing vertebrate groups, including birds, frog and mammals. The new paper shows that turtles were not categorized as vocal in the earlier study, which appears to have changed the conclusions of the 2020 analysis.

In order to tune in to the secret vocal life of turtles, he had to visit wildlife institutions in five countries. He looked at lungfish, caecilians, and tuatara, lizards that are endemic to New Zealand.

Each species was recorded for at least 24 hours. In order to capture the breadth of social situations the animals might face, he recorded them in both isolation and different groupings: females only, males only, mixed sex couples and individuals of different ages. The laborious task of sifting through more than 1,000 hours of audio was undertaken by the man after he collected the recordings.

He discovered that every species produced some sort of sound. Depending on the situation, many had different noises. Thirty different vocalizations were produced by the South American wood turtle. Some species produced a lot of sounds, while others only produced a few. Almost all of them have never had their vocalizations recorded.

There are some South American river turtles that are talking. The credit is given to the person, Camila Ferrara.

According to the evolutionary history of the turtle species included in the new study, vocal communication must have appeared hundreds of millions of years ago. According to the findings, this behavior did not arise independently in different animal groups, but was instead conserved over time, and is related to a common animal ancestor that lived at least 400 million years ago.

It is an important contribution, both because vocalizations from many important species are analyzed for the first time and because they lead to a convincing argument.

It is difficult to reconstruct the evolution of behaviors and acoustic communication is even more difficult. The paper gives us a lot more species to study in order to understand which parts of the neural circuits that support vocal communication are ancient and which are newer.

According to John Wiens, an evolutionary biologist at University of Arizona and co-author of the 2020 study, the turtles and other species they recorded did not prove that they were using those sounds to communicate with each other. That appears to be a big omission.

The paper focused on reanalyzing our data and coming to different conclusions.

The follow-up studies will have to be done on individual species to explore their full range of sounds.

A zoologist at the University of British Columbia, who was not involved in the work, says that the new paper is a great example that sometimes you have to look and listen instead of accepting a standard in a particular field.

Ballagh grew up in New Zealand. She heard about the vocalizations of the tuatara from her mother and other people. She encountered a lot of statements from the scientific establishment that she did not like. She points out that the researchers who made those assumptions were all based in the Northern Hemisphere.

Ballagh wants more people to follow up with more work connecting local and Indigenous sources of knowledge about the potential vocalizations for species groups that are still listed as anabsence of data. If we start to think more carefully about who we should be listening to, the data may already be out there.