Grunt, hoo, gasp, cry: chimpanzees use complex vocal communication

WASHINGTON: Scientists exploring the evolutionary origin of language have detected a vocal communication system in wild chimpanzees that is more complex and structured than previously known, with a dozen types of calls combined into hundreds of different sequences .

The researchers made more than 4,800 recordings of vocalizations produced by members of three groups of chimpanzees inhabiting Taï National Park in Côte d’Ivoire, one of the last major remnants of ancient rainforest in East Africa. West and home to a rich variety of plants and animals.

Chimpanzees, which along with their cousins ​​the bonobos are the closest living genetic relatives of humans, are intelligent and highly social apes that make and use tools and can learn some basic human signs from the language of animals. signs. Scientists have long known that chimpanzees use a variety of vocalizations in the wild, but the new study offered a comprehensive look at this intra-species communication.

“It is not a language but it is one of the most complex forms of communication described in a non-human animal,” said behavioral ecologist Cédric Girard-Buttoz of the CNRS Institute of Cognitive Sciences and lead author of the study published this week. in the journal Communications Biology.

Call types included growl, gasp growl, hoo sound, pants hoot, bark sound, gasp bark, pants, screech, gasp cry, whine, gasp roar and the non-vocal lip smacking and raspberry sounds. The researchers determined that these types of calls were used in 390 different sequences.

The order in which the chimpanzees made the calls appeared to follow rules and structure, although the study did not include conclusions about potential meanings.

“The key finding is the ability of a non-human primate to produce multiple structured voice sequences and to recombine small sequences with two calls into longer sequences by adding calls to them. This is important because it shows the premise structured communication that may have been the foundation for the evolution towards syntax in our language,” Girard-Buttoz said.

Syntax refers to the arrangement of words and phrases to construct understandable sentences.

“One of the most common sequences is the well-described sequence “pant hoot” either “hoo” plus “pant hoot” or “hoo” plus “pant hoot” plus “pant shout” or “pant bark”. Other sequences are also common like ‘hoo’ plus ‘pant grunt’ or ‘grunt’ plus ‘pant grunt.’ In general, ‘pant grunt’ and ‘pant hoot’ are the most common calls used in these sequences,” said Girard-Buttoz.

The researchers want to know if the different sequences communicate a wider range of meanings in the complex social environment of chimpanzees. They have suspicions about the potential meanings of certain vocalizations.

“We need to explore in detail the emission contexts of these vocalizations to see if it moves between single calls and sequences,” Girard-Buttoz said. “Then we need to conduct reading experiments to see if the suspected meaning matches the behavioral response of chimpanzees when they hear the call.”

Researchers aren’t sure whether chimpanzee vocal communication could be similar to the beginnings of language in the human evolutionary line. Humans and chimpanzees share a common ancestor but split into separate lineages perhaps 7 million years ago.

“The protolanguage was probably between what chimpanzees do and what humans do,” Girard-Buttoz said.

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