[lg policy] Boom! Hok! A Monkey Language Is Deciphered

[Harold Schiffman]

Boom! Hok! A Monkey Language Is Deciphered

Published: December 7, 2009
Boom boom! (I’m here, come to me!)


Florian Moellers

Krak krak! (Watch out, a leopard!)

Hok hok hok! (Hey, crowned eagle!)

Very good — you have already mastered half the basic vocabulary of the
Campbell’s monkey, a fellow primate that lives in the forests of the
Tai National Park in Ivory Coast. The adult males have six types of
call, each with a specific meaning, but they can string two or more
calls together into a message with a different meaning.

Having spent months recording the monkeys’ calls in response to both
natural and artificial stimuli, a group led by Klaus Zuberbühler of
the University of St. Andrews in Scotland argues that the Campbell’s
monkeys have a primitive form of syntax.

This is likely to be a controversial claim because despite extensive
efforts to teach chimpanzees language, the subjects showed little or
no ability to combine the sounds they learned into a sentence with a
larger meaning. Syntax, basic to the structure of language, seemed be
a uniquely human faculty.

Still, species like gibbons and whales make complex vocalizations in
which the order of the sounds seems to have some effect on their
meaning, though it is hard to say what. Dr. Zuberbühler’s team reports
deciphering some of the Campbell’s monkey’s communication system in
The Proceedings of the National Academy of Sciences.

“Krak” is a call that warns of leopards in the vicinity. The monkeys
gave it in response to real leopards and to model leopards or leopard
growls broadcast by the researchers. The monkeys can vary the call by
adding the suffix “-oo”: “krak-oo” seems to be a general word for
predator, but one given in a special context — when monkeys hear but
do not see a predator, or when they hear the alarm calls of another
species known as the Diana monkey.

The “boom-boom” call invites other monkeys to come toward the male
making the sound. Two booms can be combined with a series of
“krak-oos,” with a meaning entirely different to that of either of its
components. “Boom boom krak-oo krak-oo krak-oo” is the monkey’s
version of “Timber!” — it warns of falling trees.

There is yet another variation on this theme, Dr. Zuberbühler’s team
reports. Into the “Timber!” call, the Campbell’s monkeys insert a
series of up to seven “hok-oo” calls. The combined call indicates the
presence of other monkey groups and is heard most often when the
monkeys are on the edge of their home range.

The meaning of monkey calls was first worked out with vervet monkeys,
which have distinct alarm calls for each of their three main
predators: the martial eagle, leopards and snakes. But the vervets did
not combine their alarm calls to generate new meanings, unlike human
words that can be combined in an infinite number of different
sentences.

If the Zuberbühler team’s observations are correct, the Campbell’s
monkeys can both vary the meaning of specific calls by adding suffixes
and combine calls to generate a different meaning. Their call system,
the researchers write, “may be the most complex example of
‘proto-syntax’ in animal communication known to date.”

Dr. Zuberbühler said he planned to play back recordings of given calls
to the Campbell’s monkeys and to test from their reactions whether he
had correctly decoded their messaging system.

http://www.nytimes.com/2009/12/08/science/08monkey.html?_r=1&scp=1&sq=boom!%20Hok!&st=cse

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