Discussing Meals...

Article copied from ethologicalethics yahoo list

13 October 2005 16:52

Grunting chimpanzees are talking language of lunch
By John von Radowitz
Published: 14 October 2005


Chimpanzees may not talk like humans, but they understand the language of
lunch.
Researchers have found that chimps make different calls when given different
kinds of food.
High grunts denote a highly prized treat, such as bread, and low grunts food
of low value, such as apples.
Other chimps seem to know exactly what the calls mean.
When scientists played recordings of the noises to a chimpanzee at Edinburgh
Zoo, he searched in the appropriate places for the food in question.
Researcher Katie Slocombe, from the University of St Andrews, said: "This is
the first demonstration that chimpanzee calls function to refer to the
nature of discovered food and these calls are meaningful to fellow animals.
It shows that, by simply listening to each other's calls, chimpanzees can
infer what kind of food the caller has found.
"Our focal animal adjusted his foraging behaviour on the basis of the calls
he heard."
The scientists are planning further studies to test how specific the calls
are - whether they refer to "bread" and "apples", or merely high and low
value foods.
The calls are a demonstration of "functionally referential" signals given in
response to specific events or objects, such as a particular predator or
type of food.
Although a similar kind of communication has been found in monkey species,
until now there has been no evidence of it in any of the great apes.
This is surprising given that apes are more advanced mentally than monkeys
and more closely related to humans.
The scientists believe that the calls must have a social function since
chimps rarely produce the same kind of rough grunts when eating alone.
Observations in the wild have shown that chimps only produce grunts when
another individual approaches.
Dr Klaus Zuberb�hler, who led the research, published in the journal Current
Biology, said: "Chimps may find it genuinely unpleasant to eat without
others doing the same.
"The same seems to be the case for humans. We don't like to eat in the
presence of others who are not eating.
"In many cultures humans co-ordinate the timing of starting a meal, for
example with vocal cues such as 'bon appetit'.
"These 'rough grunt' calls are specifically produced when chimpanzees find
food.
"Subtle but consistent acoustic variation is present within this call type
and this study indicates chimpanzees use this variation to indicate the
presence of different foods. This study is special because it provides the
first evidence that listening chimpanzees are sensitive to this variation.
They seem to understand that the calls refer to the food encountered by the
caller."