Science / Animals & Nature

Chimpanzees Learn Call Conventions From Their Elders

Wild chimpanzees blow raspberries almost only while grooming. Sanctuary orphans use the same call for everything. The difference, researchers say, is learning.

Nora LindgrenAI editorial voice · 2 min read

A chimpanzee. The study tracked how 91 chimpanzees across eight communities used the raspberry call. (Charles Patrick Ewing, CC BY 2.0)

Summary

A PNAS study of 91 chimpanzees found communities use a raspberry call in settled, learned ways, the first such convention shown in great apes.

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Chimpanzees learn when to use a raspberry call from the adults around them, the first evidence of a learned vocal convention in great apes.

The PNAS study compared 91 chimpanzees in four wild communities in Ivory Coast's Taï forest and four sanctuary communities in Sierra Leone. Wild chimpanzees used the call almost only while grooming; sanctuary juveniles used it far more widely. [Chimpanzees blowing raspberries offer first evidence of learned vocal conventions in great ape communication — Phys.org (PNAS)] [Valet et al., A signal convention in natural chimpanzee communication — PNAS (DOI)]

The raspberry is an unvoiced sound, much like a person blowing a raspberry with their lips. If the call were purely instinctive, every group would be expected to use it the same way wherever it grew up. The wild and sanctuary animals, aged from birth to 55 years, did not. The researchers say chimpanzees learn not only to make a call but also when and why to use it. [Chimpanzees blowing raspberries offer first evidence of learned vocal conventions in great ape communication — Phys.org (PNAS)]

The strongest evidence came from a change inside one sanctuary group. When an adult chimpanzee was introduced, the group's use of the raspberry gradually became more consistent and began to resemble the newcomer's pattern, which suggests adults act as role models who help a community settle on shared ways of communicating. [Chimpanzees blowing raspberries offer first evidence of learned vocal conventions in great ape communication — Phys.org (PNAS)]

Richard Moore, a philosopher at the University of Warwick and a co-author, said: “In everyday communication, we use the words that we do only because our peers do too. It's communal practice that fixes their meaning, rather than features of the words themselves.” He said the same holding true for some chimpanzee calls shows more continuity between chimpanzee vocal learning and our own than previously suspected. [Chimpanzees blowing raspberries offer first evidence of learned vocal conventions in great ape communication — Phys.org (PNAS)]

The finding has limits, and the authors carry them. Chimpanzees still struggle to learn entirely new call sounds; what they appear to learn is the function of calls they already make. Senior author Catherine Crockford of the CNRS Institute of Cognitive Sciences also offers a physical possibility: grooming involves lip movements that extract parasites from another's fur, which may make this call easy to produce during grooming bouts, and communities may have settled on it independently. “We need more research to test it,” she said. [Chimpanzees blowing raspberries offer first evidence of learned vocal conventions in great ape communication — Phys.org (PNAS)]

First author Antoine Valet said aspects of chimpanzee vocal communication that seemed fixed and unlearned may be shaped by learning. Roman Wittig, director of the Taï Chimpanzee Project and a senior author, added the conservation edge: preserving wild chimpanzee populations is critical if researchers want to keep learning how far that learning goes. [Chimpanzees blowing raspberries offer first evidence of learned vocal conventions in great ape communication — Phys.org (PNAS)]

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