Chimpanzees have the extraordinary ability to produce complex vocalizations, with nearly 400 unique sequences identified by a team of scientists, describing a detailed communication system in this primate, the closest to humans.
They do not speak, of course, if we take human language as a reference.warns evolutionary biologist Cédric Girard-Buttoz, lead author of the study published in the journal Biology of communication in nature.
But chimpanzees have, according to the study, a remarkable ability to combine a reduced range of cries, twelve simple vocalizations, according to the researchers, in at least 390 unique sequences. A kind of syntax, which connects two to ten shouts, its meaning remains to be clarified. With the key to the possibility that the animal has developed the ability to associate sounds in different ways to mean different things.
We have some ideas about the meaning of certain sequences, one of which, for example, is exclusively linked to nesting, and which has no connection to the meaning of the calls taken in isolation.CNRS researcher of the Institute of Cognitive Sciences Marc Jeannerod explained to AFP.
The team, some of whose members are also affiliated with the German Max Planck Institute for Evolutionary Anthropology, worked based on nearly 5,000 recordings made from 46 wild adult chimpanzees in the Ivorian reserve of Taï National Park.
A doctoral student, Tatiana Bortolato, recorded more than 800 hours of vocalizations there over six months, which were then listed and classified with the help of encoders people. A new method, and will probably be used with other primates, such as the bonobo or the orangutan.
Twelve types of chimpanzee vocalizations include the most common wowwhether or not associated with gasping, or growling or barking.
They are known to specialists – and fans of The Planet of the Apes -and their meaning may vary in intensity. The “hou” linked to an alarm cry is louder in tone than that which is linked to rest, softer, said Mr. Girard-Buttoz. ang wow linked to a gasp is used, for example, to identify individuals.
Some animals have a vocabulary richer, monkey species with up to 38 types of calls. We can consider the vocal repertoire of chimpanzees, which are natural, as limitedstatement by Mr. Girard-Buttoz, but the species, with a very complex social life, may have found that there are sequences of a way of generate new meanings that expand their ability to communicate.
The study showed that the third part of vocalizations are sequences that combine some of the twelve calls, the whole set of which is used at one time or another. It also established the notion of order, with some crying always or almost always in the same position in a bigrama sequence that combines two cries. For example, “hou” is almost always in the first position, possibly indicating a repetitive communication structureresearcher’s statement.
Stronger, some bigrams are reused, perhaps as keywords, in longer sequences, with five or six other calls, further proof of a robust structure of this simian syntax. It remains to understand the relationship between the elements of these sequences, and in particular whether some form new meaning.
The researchers noticed differences between populations of chimpanzees in the order of calls in certain sequences, and this, very consistent, said Mr. Girard-Buttoz. This would imply the study of these vocal sequences within the group, and therefore a flexibility of this method of communication.
To do more, scientists will need to find the meaning of the sequences, with pre-sound experiments. We record the sound and play it with the monkey in the forest to study its reaction, says the researcher. The task will be daunting, given the number of sequences defined.
Source: Radio-Canada
