Orangutans use slang to ‘show off their coolness’, study suggests | Animal behaviour

Whether it is the rapidly shifting patois of teenagers or curious words found long-buried in the local argot of a rural community, our vocabularies are shaped by our social environs. Now, it seems, such influences might also be at play among orangutans.

Researchers studying the “kiss-squeak” alarm calls of wild communities of the apes in Borneo and Sumatra have found that rather than such sounds being innate and hardwired, as was long thought, orangutans are able to come up with new versions of the calls, varying in pitch and duration.

What’s more the frequency of novel calls – and whether the new versions stick – are influenced by the density of the local community.

“The way I see it is that low densities [of] orangutans have a slang repertoire that they constantly revisit and use. They are ‘conservative’, but once a new call variant is used, everyone hears it and the variant is quickly incorporated, enriching the slang,” said Dr Adriano Lameira, first author of the research from the department of psychology at the University of Warwick.

“In high density [communities of orangutans], communication is more like a cacophony. It seems ‘novelty’ is at a premium, much like in songbirds, and that individuals want to show off their coolness and how [much of a] rebel they are,” he said.

While social influences have been found to play a role in communication for animals including song birds and marmosets, the team behind the new research say it had been unclear whether the same was true for non-human apes – an important question given our own communication is influenced by such factors.

Writing in the journal Nature Ecology and Evolution, the team report how they spent 6,120 observation hours working across six research stations between 2005 and 2010, opportunistically recording orangutan kiss-squeaks from around 70 individuals.

Lameira said the different communities sometimes came up with the same new variations of the calls, although there is no known exchange between these populations, and they are very far apart.

The team found high-density communities of orangutans used a wide range of novel calls, but with a high turnover, meaning many rapidly fell out of use. By contrast small groups came up with new calls less frequently, but tended to retain novel calls when they occurred.

“We do not expect that social influence is restricted to alarm calls, these just happened to be the calls that were most immune to other possible influences,” said Lameira.

Lameira added that in addition to the new study there is growing evidence that great ape repertoires, like human languages, are composed of consonant- and vowel-like calls which can not only be carefully controlled, but combined to make syllable-like combinations that can even be used to communicate about past events.

“This new evidence cements a new view that great apes are highly desirable and unique model species to improve our [understanding] of language origin and language,” said Lameria.

Indeed the team say the new findings add weight to the idea that human language evolved gradually, with communication among our ape-like ancestors likely also influenced by social factors.

Lameira added the new study also highlighted the importance of conservation.

“Great apes and their habitat must be preserved if we are to hold any chances of unveiling further pieces of the puzzle of language evolution,” he said.

This article was amended on 21 March 2022 to correct the spelling of Adriano Lameira.

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