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Thailand tree apes use song as warning

Jan 28, 2008

Hamburg - Humans aren't the only "big apes" who use songs to impress each other. German researchers have found that gibbons in Thailand have developed an unusual way of scaring off predators - by singing to them. Literally singing for survival, the gibbons appear to use the song not just to warn their own group members but those in neighbouring areas.

The primatologists, Klaus Zuberbuhler from St Andrews University in Scotland and Ulrich Reichard of the Max Planck Institute in Germany, based their findings on two years spent in Khao Yai National Park in Thailand observing groups of gibbons.

Gibbons are renowned amongst non-human primates for their loud and impressive songs that transmit over long distances and are commonly used in their daily routine when mating pairs "serenade" every morning.

Songs in response to predators - mostly large cats, snakes and birds of prey - have been previously noted, but no extensive research into its purpose or understanding by other gibbons has been done until now.

The primatologists said, "We are interested in gibbon songs because apart from human speech these vocalisations provide a remarkable case of acoustic sophistication and versatility in primate communication.

"Our study has demonstrated that gibbons not only use unique songs as a response to predators, but that fellow gibbons understand them."

They added, "This work is a really good indicator that non-human primates are able to use combinations of calls given in other contexts to relay new, and in this case, potentially life-saving information to one another.

"This type of referential communication is commonplace in human language, but has yet to be widely demonstrated in some of our closest living relatives - the apes," the researchers told ScienceDaily.

They said, "We found that gibbons produce loud and conspicuous songs in response to predators to alert kin, both near and far - since gibbons frequently change group compositions, neighbouring groups often consist of close relatives."

The "songs" are not only aimed at their immediate family but also at neighbours some distance away.

"We found that gibbons appear to use loud 'long-distance' calls to warn relatives in neighbouring areas and that those groups responded by joining in the singing, matching the correct predator song, demonstrating that they understood the difference between calls."

The researchers concluded, "Vocal behaviour appears to function as a powerful tool to deal with immense sexual competition under which these primates operate, and it may not be surprising that they have evolved unusually complex vocal skills to deal with these social challenges.

"Not unlike humans, gibbons assemble a finite number of call units into more complex structures to convey different messages, and our data shows that distant individuals are able to distinguish between different song types and understand what they mean.

"This study offers the first evidence of a functionally referential communication system in a free-ranging ape species."

"Finding this ability among ape species, especially gibbons who in a sense bridge the evolutionary gap between great apes and monkeys, could shed light on when this ability developed in the primate lineage."

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