Wednesday, November 29, 2006

Chimps have distinctive grunts for different kinds of food

Researchers have added chimpanzees to the list of intelligent animals, which have the ability to produce their own distinctive word like calls for specific things.

According to the study in this month's Animal Behaviour, vocalizations indicate what's on the animals' minds, for chimps also do the same for bananas, mangoes and bread.

Researchers Katie Slocombe and Klaus Zuberb�hler discovered that captive chimps created referential, vocal labels for these particularly coveted foods.

"Our analyses surprisingly showed that grunts to banana, bread and mango were acoustically distinct. It is very possible, therefore, that recipients can use this information to draw inferences about the type of food encountered by the caller," Discovery News quoted Zuberb�hler, a researcher in the School of Psychology at the University of St. Andrews in Scotland as saying.

The scientists studied 11 chimpanzees at the Edinburgh Zoo, as well as a community of chimps in the wild at the Budongo Forest Reserve, Uganda.

For each group, the researchers first identified the chimps' favourite foods. For the zoo animals, the scientists were even able to determine their medium-preferred foods (grapes, plums and chow) and their least favourites (apples, greens and carrots).

Wild chimps, on the other hand seemed to favour spending most of their time on trees and feeding on a certain type of uncultivated fig.

Next, the scientists recorded the "rough grunt" calls the chimps emitted when they encountered the foods.

Computer analysis of these sounds revealed the zoo chimps repeatedly produced specific sounds linked to their favourite foods, while other calls were less distinctive.

"Grunts to highly preferred foods are more tonal and therefore easier to analyze. Hence, we cannot rule out that similar effects were also present within the medium and less preferred food items, but our acoustic analysis just did not pick it up," Zuberb�hler said.

While the scientists couldn't duplicate their findings for wild chimpanzees, they determined both captive and wild chimp calls were very similar, which Zuberb�hler said, suggested, "they were part of a universal chimp communication system when dealing with food".

Incidentally, previous studies have found that chimps produce distinct vocalizations when they encounter snakes, bullies, chimp victims and when they are hunting.

Story here.

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