Scientists have discovered for the first time that monkeys are capable of combining calls in meaningful ways.
The researchers at the University of St Andrews have found that putty-nosed monkeys share the uniquely human ability to string utterances together to convey messages.
During observations of the species in the Gashaka Gumti National Park Nigeria, Drs Kate Arnold and Klaus Zuberbühler found that the monkeys often produced strings of calls containing their two main call types. The species have two distinct calls that they use to alert each other against predators, but the researchers noticed that a particular sequence of calls appeared to mean something else entirely when strung together.
The new string of calls consisted of the species’ two basic call sounds: ‘pyows’, used to warn against a loitering leopard; and ‘hacks’, used to indicate a hovering eagle. These ‘sentences’, consisting of several pyows followed by a few hacks, appear to function as a command to the group to move away to safer terrain.
Dr Arnold said: “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.
“Observationally and experimentally 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 and sleeping sites.”
“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.”
The research was initially aimed at finding out whether male putty- nosed monkeys produce alarm calls which go beyond simply alerting other group members to danger, but which also ‘label’ the predator type. The researchers found that putty-nosed monkeys do not demonstrate this capability, instead noticing a series of calls which appeared to combine different calls to express new meanings. The more complex calls may represent an efficient way to use a restricted repertoire. Rather than creating a new sound, the monkeys can encode fresh information by combining two existing ones.
Dr Arnold continued: “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.
“This is the first good example of calls being combined in meaningful ways. 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.”
Dr Zuberbühler agreed: “To our knowledge, this is the first good evidence of a syntax-like natural communication system in a non- human species.”
‘Semantic combinations in primate calls’ by Dr Kate Arnold and Dr Klaus Zuberbühler is published in the 18 May issue of Nature.
NOTE TO EDITORS:
THE RESEARCHERS ARE AVAILABLE FOR INTERVIEW:
DR KLAUS ZUBERBÜHLER, TEL 01334 462 080; EMAIL: kz3@st- andrews.ac.uk
DR KATE ARNOLD, TEL 01334 460625; EMAIL Kate1arnold@aol.com, ka11@st- andrews.ac.uk
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