Graded or discrete? A quantitative analysis of Campbell's monkey alarm calls

Sumir Keenan*, Alban Lemasson, Klaus Zuberbuehler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)

Abstract

A standard way of describing the vocal behaviour of nonhuman primates is to classify the vocal repertoire as either graded or discrete. We analysed a large database of calls given by adult males of a primate considered a typical example for discrete vocal behaviour, the forest-dwelling Campbell's monkeys, Cercopithecus campbelli. We recorded vocal responses from several dozen individuals to their main predators, crowned eagles and leopards. Using cluster analysis techniques, we found two main call types, which were modified further by optional affixation of an inflexible vocal structure. It was possible to force the four call types into eight subtypes, with various degrees of gradedness. When taking context into account, we found that acoustically discrete and nonaffixed calls tended to be given right after discovering a predator, while acoustically graded and affixed calls were given during later parts of a predator encounter and to nonpredatory disturbances. In sum, our results suggest that classifications of primate vocal repertoires as either discrete or graded are likely to be meaningless, as communicatively relevant acoustic variation can be present within seemingly discrete call types. Crown Copyright (C) 2012 Published on behalf of The Association for the Study of Animal Behaviour by Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)109-118
Number of pages10
JournalAnimal Behaviour
Volume85
Issue number1
DOIs
Publication statusPublished - Jan 2013

Keywords

  • alarm call
  • discrete signal
  • nonhuman primate
  • graded signal
  • SYSTEM
  • vocal repertoire
  • CERCOPITHECUS-CAMPBELLI
  • DIANA
  • NONHUMAN PRIMATE
  • referential
  • BENEFITS
  • INDIVIDUAL DISTINCTIVENESS
  • WILD CHIMPANZEES
  • Campbell's monkey
  • ACOUSTIC VARIABILITY
  • Cercopithecus campbelli
  • VOCAL REPERTOIRE
  • ASSOCIATIONS

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