53 Animal Species Generally Thought ‘Mute’ Recorded Vocal Communications, Study Claims

Most people don't consider turtles to be particularly chatty or even to make any sounds at all. However, a paper released in Nature Communications discloses that at least 50 tortoise species vocalize, and several other cold-blooded vertebrates were originally believed to be silent. As a result of the evolutionary history of something like the species studied, the finding has larger implications. Researchers could trace vocal sounds from a common vertebrate ancestral species that lived 407 million years ago because these presumably silent species normally utilized sounds for communicating, as told by New Scientist.

Homo sapiens, as loudmouthed vertebrates, understand the value of communication, but the earliest forms of vocalizations are unknown. Scientists are looking to the choanocytes to see if communications systems have a common and ancient evolutionary origin. Choana is a collective of aquatic or semi-aquatic living creatures with a mouth and nose setup which allows them to breathe by trying to stick their nostrils out of the water.

These snoot breathers piqued the researchers' involvement even though, unlike noisy creatures, frogs, birds, or mammals, such vertebrates have already been largely ignored in acoustic research due to the assumption that they are non-vocal. The scientists in this latest analysis suspected that this might not be the case - and also, for 53 species, they were correct, as reported by Scientific American.

Vocal Communication Means for Animals

Vocalizations are unique noises that animals make with their nose and mouth by drawing air from their lungs, and they are used to interact with a diverse range of responses to their own and other life forms. They could be chanting to attract mates, urging to warn alliances about predatory animals, or grunting to frighten off competitors.

Such sounds have been researched in many types of animals, which include mammals, birds, and frogs, while others are assumed to be mostly or completely mute. At least, that was the presumption. The new study looked at some of these animals and discovered that many of them, after all, do vocalize.

A group led by the University of Zurich recorded and observed vocal sounds in 53 species previously thought to be non-vocal. These include 50 turtle species, continuing to expand on only a few commonly abbreviated to vocalize, as well as multiple other vertebrate clades in which no participants would have ever been recognized to vocalize - lungfishes, New Zealand-endemic reptiles known as tuataras, as well as eel-like amphibians known as caecilians.

(Photo: Gabriel Jorgewich Cohen)
Tuatara is found only on New Zealand islands and is considered living fossils. They also communicate acoustically.

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Widespread Acoustic Abilities in Land vertebrates

The study's first author, Gabriel Jorgewich-Cohen, utilized and combined a large literature-based set of data of 1,800 distinct species spanning the entire spectrum, demonstrating that vocal communication not only exists pervasive in land vertebrates but also evidence (of) acoustic qualities in several groups originally assumed to be non-vocal, as BBC reports.

The team then charted vocal communication across the vertebrate branch of life with unexpected results. Previous research had discovered spotty vocalization from across trees and concluded that perhaps the capacity had developed several times in various species. The researchers discovered that it evolved once only, but all vocalizations can trace back to a specific point of origin, thanks to the newly found speakers filling in the gaps.

Lead author Marcelo Sánchez mentioned that they were capable of reconstructing acoustic conversation as a mutual trait among these animals that is at least as old as their previous common ancestor, which lived an estimated 407 million years ago.

Till now, scientific evidence has favored a concurrent source of acoustic communication between many vertebrates because the morphology of the hearing instrumentation and its sensitivity, as well as the morphology of the vocal tract, vary significantly among vertebrates. However, based on the UZH scientists, the obtainable proof for this theory lacks noteworthy data from key species previously considered non-vocal or largely overlooked.

The new findings show that communications systems did not evolve numerous times in different clades but rather have a widely accepted and ancient evolutionary origin, as Sánchez concludes.