Subspecific Divergence in the Black Lemur's Low-Pitched Vocalizations

Abstract

Previous studies offered very preliminary information on the vocal repertoire of Eulemur macaco macaco and Eulemur macaco flavifrons. They agreed on the fact that both subspecies emit low-pitched vocalizations, called grunts, of different duration. Through all-occurrence and focal animal observations, we recorded the vocal activity of 31 black le- murs (12 E. m. macaco and 19 E. m. flavifrons) housed in 7 institutions, both in Europe and in Madagascar. We measured both temporal and spectral properties to describe long grunts quantitatively. We extracted acoustic parameters in the per- spective of the source-filter theory of sound production. From spectrograms, we measured call duration and 6 larynx- related features and, using Linear Predictive Coding spectra, we measured four vocal tract related acoustic properties. Our quantitative analysis has statistical support for the classification of long grunts. Using individual mean values and multi- variate Discriminant Function Analysis we have been able to successfully classify 96.8 % of the vocal signals to the sub- species of the emitter. Acoustic cues of both larynx-related and vocal tract-related acoustic parameters offered support for sub-specific recognition potential. However, univariate analyses showed that formants should be providing listeners with subspecies-specific information.