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It’s not gibberish — gibbons have a secret language

LONDON — Gibbons have a secret language that contains “words” for animals such as leopards and eagles, scientists have found, in a discovery that sheds light on the evolution of human speech.

A white-handed Gibbon baby jumps towards his mother in its enclosure at Schoenbrunn zoo in Vienna May 7, 2010. REUTERS/Leonhard Foeger (AUSTRIA - Tags: ANIMALS)

A white-handed Gibbon baby jumps towards his mother in its enclosure at Schoenbrunn zoo in Vienna May 7, 2010. REUTERS/Leonhard Foeger (AUSTRIA - Tags: ANIMALS)

LONDON — Gibbons have a secret language that contains “words” for animals such as leopards and eagles, scientists have found, in a discovery that sheds light on the evolution of human speech.

The apes that were studied in Thailand made 450 distinctive “hoo” calls — softer calls or, essentially, ape whispers — in response to particular events or the presence of predators, and scientists at Durham University translated those calls so they could tell what the creatures were, literally, gibbering on about.

Though scientists have known about these soft calls since the 1940s, they are so quiet that it has been hard for the human ear to distinguish between the sounds or even record them so they could be analysed. However, increasingly sensitive recording equipment has now, for the first time, allowed researchers to monitor the whispers, opening up astonishing insight into the gibbons’ sophisticated communication.

The apes make specific sounds when foraging or encountering neighbours and can even distinguish between different predators, making warning noises when a particular animal comes too close. They have managed to keep their calls beneath the hearing ranges of their predators so they can communicate the danger without being heard.

The scientists, whose findings were published in the journal BMC Evolutionary Biology, spent almost four months following lar gibbon groups around the forests of north-eastern Thailand, staying with the primates from early in the morning until they had located their evening sleeping tree. Researchers recorded their hoos and noted the event that elicited the response. From the recordings, they extracted more than 450 different hoo sounds and used computer analysis to find links between audio patterns and the context in which they were recorded.

The team found that there were different calls, or “words”, for a range of predators, including leopards, tigers, pythons and eagles. The whispers even distinguished between different types of birds that were physically similar, such as eagle owls and serpent eagles. The bird calls were the quietest, below 1 kHz, and which raptors would struggle to hear. Tiger and leopard hoos were similar, suggesting that callers perceived these two predators as belonging to the same “big cat” class.

The scientists believe the acoustic variation heard in gibbon hoos may be similar to human speech, in which pitch can be important carriers of meaning. Lead author, Dr Esther Clarke, said: “These animals are extraordinarily vocal creatures and give us the rare opportunity to study the evolution of complex vocal communication in a non-human primate.

“In the future, gibbon vocalisations may reveal much about the processes that shape vocal communication and because they are an ape species, they may be one of our best hopes at tracing the evolution of human communication.” THE DAILY TELEGRAPH

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