A new methodological approach to context analysis of call production
Résumé
There is a need to improve the assessment of causes and consequences of vocal behaviour. The lack of descriptions of the context of call or song production comes from the complexity of its definition. The context is composed of numerous physical and social parameters and therefore its analysis should be multi-dimensional. Classical approaches involve a relatively subjective data reduction. This is due to a pre-selection of the parameters which may be potentially involved, as the analysis becomes rapidly complicated when the number of factors increases. This paper describes a helpful method that allows a much wider range of potential parameters to be explored and displayed visually. The parameters selected for subsequent analysis are those indicated by the display as most relevant and are therefore not arbitrary. We applied this method to observations of events (external or internal to the group) or behaviours (including postures) preceding and following call production. Calls of Campbell's monkeys Cercopithecus campbelli present call types composed of several stereotyped sub-types, raising the question of whether or not such variations have a functional meaning for animals. We present three examples of the application of this method to describe in detail the context of production of a given call type, to detect specific temporal sequences of production and to discriminate between structurally close sub-types.