Orangutans Use Leaves to Sound Bigger
A Bornean orangutan. Courtesy of Flickr user Graham Racher
An orangutan will produce an alarm call known as a “kiss squeak” when it encounters a predator like a snake or a human. The kiss squeak is produced by drawing a sharp intake of air through pursed lips (see this video for an example). Sometimes, though, an orangutan will take a branch, strip the leaves from it, hold the leaves in front of its mouth and then make the sound. Why?
Researchers studying the wild Bornean organutan (Pongo pygmaeus wurmbii) recorded kiss squeaks made by the animals near a research station. (Their study appears in the Proceedings of the Royal Society B.) They found that the leaves lowered the maximum frequency of the sound (i.e., made it deeper). Also, smaller orangutans were more likely to use the leaves.
The orangutans appear to be using the leaves to make themselves sound like they are bigger than they really are. The scientists say that this is the first case of an animal using a tool to manipulate sound.
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Orangutans are critically endangered in the wild because of rapid deforestation and the expansion of palm oil plantations.
If nothing is done to protect these majestic creatures, they could be extinct in just a few years.
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Comment by Richard Zimmerman — August 6, 2009 @ 2:03 pm
[...] image: A Bornean orangutan. Courtesy of Flickr user Graham Racher (via Smithsonian.com) [...]
Pingback by Tool Use in Wild Orang-utans Modifies Sound Production: A Functionally Deceptive Innovation? – Proc. R.Soc B. « Anthropology.net — November 25, 2009 @ 3:11 am