August 5, 2009
Orangutans Confuse Predators With Leaves
A new study shows that wild orangutans in Borneo hold leaves to their mouths to make their voices sound deeper than they actually are.
According to the scientists that observed the apes, the animals employ the leaf trick when predators threaten them.
Holding leaves to their mouths enables the orangutans to lower the frequency of the sound they make.
This strategy makes the apes appear to be a bigger target than they are to the predator.
The apes make the sounds in response to approaching snakes, clouded leopards, tigers or humans.
This distress call has been labeled as "kiss squeaks" because the sound, which is made by a sharp intake of breath through pursed lips, produces a similar sound made during a kiss.
Using leaves to modify the sound deceives 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 this study suggests that primate-calling behavior is not only based on instinct, but it is also socially learned.
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