Preliminary results of a detailed acoustic analysis of vocalisations in a captive group of Varecia variegata variegata are discussed. Digital audio and video recording of naturally occurring vocalisations of this species were collected at the St. Louis Zoo. The sound recording equipment included a Sony TCD-D8 DAT recorder with a Sony ECM-MS907 microphone. Sound recordings were processed with Sonic Foundry SoundForge 4.5 and analysed with Voxys 3.1 for PC. Comparative analyses of affiliative vocal communication in Varecia variegata variegata revealed significant differences in frequency modulation between Mews and Whines. Statistical categorisation based on the first harmonic and the modulation of the fundamental and the first harmonic correctly assigned vocalisations to their predicted categories (100% accuracy). Univariate analysis underlined that differences between Mews and Whines (Gamba et al. 2000: Folia Primatologica: 71, 297) consist mainly of frequency modulation.. Investigating both modulated and stable parts of the signals, we show there is no difference in this group between spectral measures of the stable portion of Mews and Whines, but significant differences between the modulated parts. The fundamental frequency, first and second harmonics and most of the parameters related to frequency modulation were significant. Vocalisations of juveniles (3 and 11 months-old) differ significantly from adults' in the lndex of Harmonicity measured in the stable portion of the signals.
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