ScienceDaily (Dec. 13, 2009) — A study carried out in Ivory Coast has shown that monkeys of a certain forest-dwelling species called Campbell's monkeys emit six types of alert calls. The primates combine these calls into long vocal sequences which allow them to convey messages about social cohesion or various dangers, including predation.

Female Cercopithecus campbelli campbelli in captivity. (Credit: Copyright A. Laurence)

These results, obtained by researchers at the Ethologie Animale et Humaine research group (CNRS / Université Rennes 1), working with the universities of St Andrews in Scotland and Cocody-Abidjan in Ivory Coast, were published on the website of the Proceedings of the National Academy of Sciences. The results reveal the most complex example of "proto-syntax" yet discovered in a non-human species.

For two years, at the Taï Monkey Project research station in the Taï national park in Ivory Coast, researchers studied the behavior of Campbell's monkeys (Cercopithecus campbelli campbelli). These monkeys live in small groups of ten or so individuals, made up of an adult male, several adult females and their progeny.

Researchers from the Ethologie Animale et Humaine research group (CNRS / Université de Rennes 1), working with a psychologist and an ethologist from the universities of St Andrews in Scotland and Cocody-Abidjan in Ivory Coast, studied the loud calls of adult males, whose vocal repertory is very different from that of females. They observed the vocal response of males to various disturbances of their environment, notably encounters with natural predators (like the eagle and leopard). They also carried out visual simulation experiments (with stuffed leopards and eagles) as well as acoustic experiments (using a loud-speaker amplifying leopard or eagle calls and grunts) suggesting the presence of these predators.

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