Nov. 28, 2006 — Whales do it. Chickens do too. And now chimpanzees can be added to the list of animals that appear to produce distinctive word-like calls for specific things, according to a study in this month’s Animal Behavior.
If such vocalizations indicate what’s on the animals’ minds, then for zoo chimps it’s bananas, mangos and bread. Researchers Katie Slocombe and Klaus Zuberbühler discovered that captive chimps likely create referential, vocal labels for these particularly coveted foods.
"Our analyses surprisingly showed that grunts to banana, bread and mango were acoustically distinct," Zuberbühler, a researcher in the School of Psychology at the University of St. Andrews in Scotland, told Discovery News. "It is very possible, therefore, that recipients can use this information to draw inferences about the type of food encountered by the caller."
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' favorite foods. For the zoo animals, the scientists were even able to determine their medium-preferred foods (grapes, plums and chow) and their least faves among food regularly offered (apples, greens and carrots). The wild chimps seemed to feed most often on certain trees, including a type of uncultivated fig tree.
The scientists next 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 food faves, but that other calls were less distinctive.
"Grunts to highly preferred foods are more tonal and therefore easier to analyze," Zuberbühler explained. "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."
