A combined team of linguists and primatologists analysed alarm calls of Campbell's monkeys on two sites: the Tai forest in Ivory Coast and Tiwai Island in Sierra Leone. Monkey predators on the two sites differ: the primates are threatened by eagles on Tiwai Island and by eagles and leopards in the Tai Forest.
    
"Our findings show that Campbell's monkeys have a distinction between roots and suffixes, and that their combination allows the monkeys to describe both the nature of a threat and its degree of danger," said the study's lead author, Philippe Schlenker, a Senior Researcher at Institute Jean-Nicod within France's National Center for Scientific Research (CNRS) and a Global Distinguished Professor at New York University.
    
Using transcriptions of monkey calls gathered in field experiments involving playbacks of predator calls (eg eagle shrieks and leopard growls), the researchers found greater complexity in expression than previously understood as well as differences in alarm calls between the two locations.Their analysis showed that these calls make a distinction between roots (especially 'hok' and 'krak') and suffixes, and that their combination allows the monkeys to describe both the nature of a threat and its degree of danger.
    
For instance, 'hok' warns of serious aerial threats-usually eagles- whereas 'hok-oo' can be used for a variety of general aerial disturbances; in effect the suffix -oo serves as a kind of attenuator, researchers said.The results also suggest that the calls are not used in the same way in the Tai Forest and on Tiwai Island. For instance, 'krak' usually functions as a leopard alarm call in Tai, but as a general alarm call - to warn of all sorts of disturbances, including eagles - on Tiwai. The study appears in the journal Linguistics and Philosophy.

 

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