Song structure and sex specific features in the indris

Abstract

In the dense tropical rainforests of Madagascar, visual communication is impeded by obstacles. Lemurs use scent marking to communicate at a short distance and loud calls to communicate at a long range. The Indri (Indri indri) is a diurnal primate that emits choruses of three distinct types. The song types are essential in advertising position within the group territory, in deciding the sorts of aggressive group encounters, and in maintaining cohesion between animals dispersed during feeding. A detailed examination of the advertisement songs showed that three main parts constitute them. The last, most consistent of these parts, showed phrases consisting of units emitted with a descending frequency. The rhythm of these units changed significantly between phrases of different durations and the sexes. We also found that the unit structure may provide conspecifics with information on the individual identity of the emitter and that male songs, but not female’s, are more similar to those of their parent of the same sex than to other indris. The song of the indris is an effective way to transfer information at a long distance and may transmit sex and individual identity information.