Tonal calls, noises and its associations in Eulemur species [abstract]

Marco Gamba & Cristina. Giacoma (2002). Tonal calls, noises and its associations in Eulemur species [abstract]. Bioacoustics, Volume 13 (2): 181 -182

It is widely known that most of the lemur vocal repertoires are poorly studied or even completely undescribed. Recent analysis of Eulemur vocal repertoires from the phonetic point of view allow the categorisation of tonal calls, noises and composite emissions of different subspecies and species. These developments suggest that, for understanding the evolution of the Eulemur vocal repertoire, comparative analysis of the vocal repertoires of captive specimens provides a viable method to study species relationships and therefore to identify the developmental processes that underlie evolutionary change. In this work we discuss results from a comparative acoustic analysis of vocalisations in Eulemur rubriventer, Eulemur macaco (E. m. maccco, E. m. Flavifrons), Eulemur coronatus, Eulemur mongoz and Eulemur fulvus. Detailed acoustical analysis was necessary to generate data for the classification of the naturally occurring vocalisations. This classification is essential to figure out which vocal types could be compared and to make a preliminary description of the vocal repertoires. Digitised calls were categorised and then statistically analysed. We measured 40 different acoustic parameters per vocalisation, including dominant frequency, four spectrum peaks, index of formant dispersion, duration and harmonic composition. We found three main categories: at single unit, simple structure (featuring Tonal calls, Snorts, Gulps);  b) multiple unit, simple structure (featuring Grunts, Long Grunts, Hoots); c) multiple unit, complex structure (Snort- Grunt- Clear Calls, Grunt -Clear Calls, Snort-Grunt, Long Grunt -Clear calls, Rising Grunts). Moreover, the vocal repertoires are quite divergent among species of lemurs that are closely related; these results suggest that differences in the phonatory apparatus and in their social behaviour have been underestimated.