THE VOCAL REPERTOIRE OF BARBARY MACAQUES - A QUANTITATIVE-ANALYSIS OFA GRADED SIGNAL SYSTEM

The vocal behavior of Barbary macaques (Macaca sylvanus) was studied i n an outdoor enclosure at Rocamadour, France. Ad libitum recordings we re made across a broad array of socioecological contests from 92 indiv idually identified subjects from all age-sex classes. From the recordi ngs, 8479 calls were sampled and submitted to a Fourier transform. A c ustom software program was used to determine 35 acoustic parameters de scribing the call in terms of its frequency and time dynamics. On thes e parameters a cluster analysis was used to examine the acoustic morph ology of the Barbary macaque vocal repertoire. The analysis revealed a highly graded structure with intergraded variations between different clusters ('call types'). There were clear age-related preferences in usage of different clusters, but animals of all ages were potentially able to produce the whole array of call types. The major sex differenc e was a differential use of certain call types in specific situations. Despite a clear sex dimorphism in body size no significant sex differ ences in the acoustic structure of calls in adults was found. There we re no unidirectional relationships between the acoustic structure of a call and the context in which it was uttered, although call usage was more specific in some contexts than in others. The results suggest th at the major factor underlying the variation in acoustic structure ref lect the internal state of the caller.