VARIATION IN PRIMATE VOCALIZATIONS AND PRIMATE SONGS: EFFECTS OF SPECIES, SEX, INDIVIDUALITY, AND PHONATORY PROCESS

Acoustic cues in vocalizations may play a role in individual, sex and species recognition, and are presumably crucial in courtship and social and competitive behaviors in all primate species, including lemurs. I investigated the relationship between vocal measurements (fundamental and formant frequencies) and phonation process in Lemuridae and Indridae, across the vocal repertoire. Acoustic analyses suggest that spectral parameters could provide lemurs with the information necessary to recognize conspecifics. Physical measures of the vocal tract were then used to build computational models, which allowed investigating the effect of body size variation within and between different species. Estimated natural body size variation appears as an important factor in providing species-specific cues to congeneric listeners. However, across different genera resonance in the vocal tract generate distinct formant patterns strongly related both with the vocal tract shape and with its relative length. I’ll then focus on Indri indri, a peculiar species of singing primates. Males and females within a social group sing together in coordinated choruses, as it happens in Gibbons. I will show differences and similarities between male and female singing behaviors in term of timing, repertoire size, syntactical structure and acoustic features of the utterances. I will illustrate sex-specific and individual-specific acoustic patterns characterizing the long distance calls of indris.