According to National Geographic News researchers at the University of St. Andrews in Scotland have discovered that chimps use certain distinctive grunts to communicate about food:
At the Edinburgh Zoo the chimps make high grunting noises when they find bread, a food they seem to like, and low grunting sounds when they find apples, which they apparently don't care for very much, according to the study, published last week in the journal Current Biology.
After noting the different types of grunts, the researchers set out to see if other chimps listening to the grunts interpreted them the way the researchers had ("bread" and "apple"). The researchers found that the listening chimp did seem to understand what the grunts mean.
The scientists recorded the grunts and played them to a chimp in the pen. When the chimp heard the "bread" grunt, the ape looked in the place in the pen where bread is usually found. When the "apple" call was played, the chimp searched appropriately for an apple.
"It shows that, by simply listening to each other's calls, chimpanzees can infer what kind of food the caller has found," said researcher Katie Slocombe, who worked with colleague Klaus Zuberbuhler on the project.
The researchers argue that these calls are referential signals but caution that:
"We don't know yet how specific these calls are—i.e., whether they specifically refer to bread or apples or whether they simply label highly preferred food [such as bread] and less preferred food types [such as apples]. We are planning further experiments to test these two possibilities," Slocombe said.
Over and above the issue of language, there may be another social function to these grunts:
Study co-author Zuberbuhler believes that the grunts serve a social function, since the chimps hardly ever make the noises when they are eating alone.
The grunts may be a call to dinner, Zuberbuhler says. "Chimps may find it genuinely unpleasant to eat without others doing the same."
The possible dinner-bell grunts may be related to certain human vocalizations, Zuberbuhler said.
"We don't like to eat in the presence of others who are not eating," he said.
"In many cultures humans coordinate the timing of starting a meal, for example, with vocal cues such as 'bon appetit.'"
I, for one, can't wait to see the results of the planned follow up research.