The #1 source for news about monkeys and apes

[Josh Greenman <josh.greenman AT gmail.com>]

http://news.bbc.co.uk/2/hi/science/nature/8184015.stm

Orangutan ruse misleads predators

Wild orangutans in Borneo hold leaves to their mouths to make their
voices sound deeper than they actually are, a new study shows.

The apes employ the leaf trick when they are threatened by predators,
according to scientists observing them.

By holding leaves to their mouths, the orangutans lower the frequency
of the sounds they produce.

This is used to ward off predators, giving them the impression the
apes are a bigger target.

The international team made the discovery while observing distress
calls made by the orangutans.

The apes make the sounds in response to approaches by snakes, clouded
leopards, tigers or humans.

These distress calls are known as "kiss squeaks" because they involve
a sharp intake of breath through pursed lips, producing a sound
similar to that made during a kiss.

But by using the leaves to modify the sound that comes out, orangutans
deceive predators into thinking the calls are being made by a bigger
animal.

Co-author Madeleine Hardus, from the University of Utrecht in the
Netherlands, told BBC News: "This study clearly indicates that the
abilities of great ape communication have been traditionally
undervalued and that there may be traces of language precursors in our
closest relatives, the great apes."

She added that the findings suggest that primate calling behaviour is
not purely based on instinct, but instead is socially learned.