The vocalizations of turtles upset the history of acoustic communication


MBut what fly had stung Jean de La Fontaine’s hare? Pass again to mock the slowness of the tortoise, but to treat it of “gossip” ! The naturalists are however formal: the turtles remain silent. Or so we thought until October 25. In an article published in the journal NatureCommunicationsan international team claims to have highlighted a “acoustic communication” in no less than fifty species of chelonians, their scientific name. A big step in the knowledge of this order of reptile. A leap in understanding the origins of sound communication in vertebrates.

For Gabriel Jorgewich-Cohen, it all started with the observation of his own pet turtles and the desire to dig behind their shell. Among the questions that torment him then, there are these little sounds that he perceives. A study trip to the Amazon finally convinced the student from the University of Zurich (Switzerland) that he had an important subject there. He will devote his thesis to the distribution of “acoustic communication” among the three hundred and ten listed species.

To cover the entire spectrum, the zoologist selects fifty, freshwater, marine and terrestrial. “Many are rare and endangered”, he says. So there is no question of disturbing their habitat. Even less to take them to isolate them and make sure that the recorded sounds do not come from elsewhere. It is therefore a real world tour of institutions in which he devotes himself for two years.

The result is impressive: in all the species studied, his team found acoustic signals. More or less frequent, more or less powerful, but “every recorded species has produced sounds”. What concludes that all turtles vocalize? “I would be very surprised if we discovered that some do not”advances the researcher.

Appearance in a common ancestor

The team went above and beyond. First, she recorded three cousin species of turtles: a lungfish named lungfish; a tuatara, a species of New Zealand lizard; and a caecilia, a legless amphibian. All sound, again. Finally, the researchers took up the literature and more particularly the data relating to 1,799 species of tetrapods collected in 2020 by John Wiens, of the University of Arizona. In an article published in the same journalafter a methodical phylogenetic analysis, the biologist concluded that acoustic communication had appeared in parallel, on several occasions, in these different groups, 100 to 200 million years ago.

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