Monkeying around with warning calls

Making different sentences out of the same words was thought to be a unique feature of human language but scientists have now discovered syntax in monkeys.

A study of wild putty-nosed monkeys in Africa has found that they can mix different alarm calls to communicate new meanings to fellow members of a troop.

Scientists found that the two basic sounds - "pyows" and "hacks" - which are used to warn against different predators can be combined to mean something quite different.

The monkeys call out "pyows" to warn against a loitering leopard and "hacks" are used to warn about hovering eagles overhead.

However, combining "pyow" and "hack" means something like "let's go", according to scientists from the University of St Andrew's.

"To our knowledge, this is the first good evidence of syntax-like natural communication system in a non-human species," said Klaus Zuberbuhler, one of the researchers.

The putty-nosed monkeys in the study live in the Gashaka Gumti National Park in Nigeria and were frequently heard using different sounds in response to different threats. Kate Arnold, the other member of the team, said that she became aware that the monkeys used several "pyows" followed by a few "hacks" as a way of telling a group to move away to safer terrain.

"These calls were not produced randomly and a number of distinct patterns emerged. One of these patterns was what we have termed a 'pyow-hack sequence'.

"This sequence was either produced alone or inserted at certain positions in the call series," Dr Arnold said.

"We have demonstrated that this call sequence serves to elicit group movement in both predatory contexts and during normal day-to-day activities such as finding food sources," she said.

The scientists demonstrated in a study published in Nature that they would imitate the communication syntax of the monkeys by playing recorded calls to the wild troop living in the forest.

"The 'pyow-hack' sequence means something like 'let's go' whereas the 'pyows' by themselves have multiple functions and the 'hacks' are generally used as alarm calls," Dr Arnold said.

"Previously, animal communication systems were considered to lack examples in which call combinations carried meanings that were different to the sum of the meanings of the constituent elements," she said.

"This is the first good example of calls being combined in meaningful ways," Dr Arnold said.

"The implications of this research are that primates, at least, may be able to ignore the usual relationship between an individual call and any meaning that it might convey under certain circumstances."

- INDEPENDENT