Whether it’s the rapidly changing patois of teens or curious words long found hidden in the local argot of a rural community, our vocabulary is shaped by our social environment. Now it seems that such influences may also play a role in orangutans.
Researchers studying the “kiss-peak” alarm calls of wild monkey communities in Borneo and Sumatra have found that rather than such sounds being innate and tethered, as was long thought, orangutans are developing new versions of the calls. can think of, varying in pitch and duration.
In addition, the frequency of new calls – and whether the new versions stick around – is affected by the density of the local community.
“The way I see it is that low densities [of] orangutans have a snake repertoire that they constantly revisit and use. They are ‘conservative’, but as soon as a new bell variant is used, everyone hears it and the variant is quickly absorbed, enriching the jargon,” said Dr Adriano Lameira, lead author of the study from the Department of Psychology at the University of Warwick .
“In high density [communities of orangutans], communication is more of a cacophony. It seems that “novelty” is highly valued, as with songbirds, and individuals want to show off their coolness and how [much of a] they are rebellious,” he said.
While social influences have been found to play a role in communication for animals, including songbirds and marmosets, the team behind the new study say it was unclear whether the same was true for non-human monkeys — an important question given our own communication is influenced by such factors.
In the journal Nature Ecology and Evolution, the team reports how they spent 6,120 observation hours working at six research stations between 2005 and 2010, opportunistically recording orangutan kissing sounds from about 70 individuals.
Lameira said the different communities sometimes came up with the same new variations of the calls, although there is no interchange between these populations and they are far apart.
The team found that high-density orangutan communities used a wide variety of new calls, but with high turnover, meaning many quickly fell out of use. In contrast, small groups were less likely to come up with new calls, but tended to hold new calls when they arose.
“We don’t expect social influence to be limited to emergency calls. These happened to be the calls most immune to other possible influences,” Lameira said.
Lameira added that alongside the new study, there is mounting evidence that great apes repertoires, such as human languages, are composed of consonant- and vowel-like calls that can not only be carefully controlled, but combined to create syllable-like combinations that can even be used to communicate about past events.
“This new evidence confirms a new view that great apes are highly desirable and unique model species for our [understanding] of language origin and language,” said Lameria.
Indeed, the team says the new findings add weight to the idea that human language evolved gradually, with communication between our ape-like ancestors likely also being influenced by social factors.
Lameira added that the new study also emphasized the importance of conservation.
“The great apes and their habitat must be preserved if we are to keep the opportunity to reveal further pieces of the puzzle of language evolution,” he said.