Young chimpanzees learn the raspberry call from adults, a PNAS study of 91 apes in Ivory Coast and Sierra Leone finds
Wild and sanctuary chimpanzees use the raspberry call in different situations, and a newly introduced adult shifted a group's usage. The call's use appears learned, not innate.
Chimpanzees may learn how to use some of their calls from the adults around them, a parallel with how human children learn words. This is reported in a study by the CNRS Institute of Cognitive Sciences, the University of Warwick and the Taï Chimpanzee Project, published in PNAS and described by eurekalert.org. eurekalert.org
eurekalert.orgeurekalert.orgOpen source ↗
Until now, scientists have assumed that chimpanzee calls are largely instinctive and fixed by biology. The new work tests this for the first time. The team compared how 91 chimpanzees, aged from birth to 55 years, used the raspberry call, an unvoiced sound similar to a person blowing a raspberry with the lips.
Wild and sanctuary groups differ
The researchers studied four communities of wild chimpanzees in Taï National Park, Ivory Coast, and four communities of orphaned, peer-raised chimpanzees at Tacugama Chimpanzee Sanctuary in Sierra Leone.
Wild chimpanzees used the raspberry almost exclusively while grooming others. The juveniles at the sanctuary used it across a much wider range of social situations. eurekalert.org
eurekalert.orgeurekalert.orgOpen source ↗ If the call were purely instinctive, groups would be expected to use it in similar ways wherever they grew up. According to the authors, the differences suggest that chimpanzees learn not only to make a call, but also when and why to use it.
Adults as role models
When an adult chimpanzee was introduced to one of the sanctuary groups, the group's use of the raspberry gradually became more consistent and began to resemble the newcomer's. The authors say this suggests adults act as role models, helping a community settle on shared patterns of communication.
The researchers state that this is the first time such learned, agreed use has been shown in chimpanzee calls. The link between the sound and its use appears to be passed from one chimpanzee to another rather than built in at birth.
Unlike humans, chimpanzees struggle to learn entirely new call sounds. The findings suggest, however, that they can learn the functions of calls they already make. eurekalert.org
eurekalert.orgeurekalert.orgOpen source ↗ "Even aspects of chimpanzee vocal communication that seemed fixed and unlearned may be shaped by learning, suggesting that there is still much to discover about their vocal repertoire," said first author Antoine Valet.
The paper, "A signal convention in natural chimpanzee communication," is published in PNAS (DOI: 10.1073/pnas.260683712). The work was led by doctoral student Antoine Valet with a team headed by Catherine Crockford at the CNRS Institute of Cognitive Sciences in Lyon and the Taï Chimpanzee Project.
