Friday, March 14, 2008
'Pyow-pyow': how the putty-nosed monkey tells its friends there's a leopard coming
Putty-nosed monkeys combine signals in a limited repertoire to convey complex messages. But see below, Howlers are also great talkers.
A troop of monkeys in west Africa has been found to use different combinations of calls to convey different meanings in what is believed to be one of the first experimental demonstrations of rudimentary language ability in wild animals.
The putty-nosed monkeys living in Nigeria were already known to use different alarm calls to warn each other about the presence of predators, but now scientists have found that their linguistic ability goes a step further.
Male putty-nosed monkeys are able to combine different types of alarm calls to indicate their identity, what they have seen and whether they intend to flee – and all of this information is recognised by other members of the troop, a study has found.
Klaus Zuberbühler, of St Andrew's University, said his research into wild putty-nosed monkeys demonstrated that their linguistic ability shows intriguing similarities with human speech, in that they can combine sounds to convey various meanings. "In linguistics, 'morphemes' are usually defined as the smallest meaningful units in the grammar of a language. Our research revealed some interesting parallels in the vocal behaviour of forest monkeys and this feature of human language," he said.
The monkeys have two basic alarm calls – "hacks" and "pyows", and they use them to warn each other about different predators – for example, a "pyow-pyow" signals a leopard. Dominant male monkeys are also able to combine "hacks" and "pyows" into a unique sequence that conveys important information, such as "I am about to travel, follow me", according to Dr Zuberbühler, who, with his colleague Kate Arnold, carried out the study published in the journal Current Biology.
The scientists proved their theory by playing audio tapes of "pyow-hack" sequences made by a dominant male and observing the reactions of other troop members. The behaviour of the monkeys followed the scientists' predictions – for instance, that they would all move in response to the signal to travel.
"What we showed is that it was this call sequence alone that was sufficient to trigger group travel," Dr Zuberbühler said. "Most primates are limited in the number of signals they can physically produce due to their lack of tongue control. The only way to escape this constraint may be to combine the few calls they have into more complex sequences.
"In other words, it may be harder for non-human primates to evolve large repertoires than to evolve the ability to combine signals. Hence, the evolution of combinatorial signaling may not be driven by too many signals, but rather by too few."
The ability to combine different sounds or vocalization was believed to be an important step in the evolution of human language. According to this theory, at some point it became more economical to combine existing elements of communication, rather than adding new ones, because the repertoire was already too large.
But, Dr Zuberbühler said: "Our research shows these assumptions may not be correct. Putty-nosed monkeys have very small vocal repertoires, but nevertheless we observe meaningful combinatorial signalling."
* The study of the putty-nosed monkey was carried out in the Gashaka Gumti National Park in Nigeria.
* Naturalists observed the animals using two distinct alarm calls – "pyow" and "hack" – in non-random sequences.
* Further studies revealed that the monkeys were using different combinations of calls to express various specific meanings.
* These include: hack-hack-hack-hack: "There's an eagle over there!"
* Pyow-hack-hack-pyow-pyow-pyow: "I've seen a leopard, let's move away!"
* Hack-hack-hack-pyow-hack-hack-hack-hack-hack "There's an eagle over there, let's move away!"
Yes Howlers do talk and do communicate vocally.
I first noticed the ability to vocalize needs in Howler monkeys, many years ago. We notice that when a monkey had been separated from its parents it suffered great grief for several weeks. This was demonstrated by pacing up and down in its enclosure and repeating the same sounds over and over again. The sound approximated to (what oh) with the ‘oh’ drawn out for at least two seconds. Following that we notice a sound indicating pleasure, especially when a desired food was presented, although it can accompany any pleasurable experience like being with a friend (human or monkey) or place that makes them feel happy. A repeated whoop whoop whoop sound indicates danger and displeasure, this is not necessarily a message to the troop it can be just an indication of displeasure. Remember that Howlers have a special extension to their hypoid bone. In their case it is very large and allows a great noise that can carry for up to 3 km. This also means that the sounds that they make are fairly deep throated. The thing which I have found most extraordinary is that this language is universal. We have monkeys here in our facility that come from all over but the language is just the same. They have many expressions and they do have the ability to produce quite a range of different sounds. I would really like to find a research student with the interested to analyze their language. I do not have formal linguistic analytic ability but I would love someone to do this work. Yes Howlers do talk and do communicate vocally.
Posted by Philip Cordrey at 4:24 PM