Wild orangutans have a language with complex vocal signals and gestures, allowing the creatures to communicate rapidly to each other.
University of Exeter scientists identified 11 vocal signals and 21 physical gestures, such as pushing out a lower lip, shaking objects and ‘presenting’ body parts.
The animals use these sounds and gestures to communicate ideas and requests such as “climb on me”, to each other - or to say “stop that”.
The animals react quickly, responding with more gestures or sounds in less than a second in 90 percent of cases.
Sounds included the “kiss squeak” (a sharp kiss noise created while inhaling), the “grumph” (a low sound lasting one or two seconds made on the inhale), the “gorkum” (a kiss squeak followed by a series of multiple grumphs), and the “raspberry”.
“We observed orangutans using sounds and gestures to achieve eight different ‘goals’ – things they wanted another orangutan to do,” said University of Exeter scientist Dr Helen Morrogh-Bernard, founder and co-director of the Bornean Nature Foundation (BNF).
“Orangutans are the most solitary of all the apes, which is why most studies have been done on African apes, and not much is known about wild orangutan gestures.
“We spent two years filming more than 600 hours of footage of orangutans in the Sabangau peat swamp forest in Borneo, Indonesia.
“While some of our findings support what has been discovered by zoo-based studies, other aspects are new – and these highlight the importance of studying communication in its natural context.”
One of the new findings is that while orangutans favour hands over feet when making gestures, they use their feet more than chimpanzees for this purpose.
Video footage of 16 orangutans (seven mother-child pairs and a pair of siblings) yielded a total of 1,299 communicative signals – 858 vocal signals and 441 gestures.
The researchers say more signals are likely to be identified in the future.
Vocal communication increased when the other orangutan was out of sight.