Singing lemurs may use a soprano-like trick to project songs

When opera singers attempt high notes, subtle alterations in mouth and throat shape enable their voices to travel greater distances. New research reveals that a rare creature in Madagascar, the singing lemur, may utilize a similar vocal technique in its dense rainforest habitat. In the northeastern forests of Madagascar, where thick vegetation obstructs visual contact beyond a short distance, the indris communicate through hauntingly beautiful songs.

Researchers have discovered that these primates widen their mouths when producing higher-pitched notes, a vocal method referred to as formant tuning. This adjustment, which alters the shape of the vocal tube, enhances the power and range of their voices, much like trained opera singers.

The study, published in the journal PLOS Computational Biology, analyzed 83 video recordings of 19 wild indris in Madagascar's Maromizaha forest and Mitsinjo reserve. By tracking facial landmarks frame by frame and synchronizing audio, researchers found a strong correlation between mouth opening and pitch. The indri's songs, described as a haunting blend of a wail and a siren, serve multiple social purposes.

Primarily, they function as territorial alerts, enabling the indris to communicate their presence across vast, forest-covered landscapes where visual contact is limited. Remarkably, these territorial songs tend to lengthen when the group encounters another group visually, suggesting that the song is reinforced by direct visual interaction.

De Gregorio, co-author of the study, emphasizes the significance of these findings, not only in highlighting the unique vocal ability of the indris but also in drawing attention to the critically endangered status of these lemurs. Lemurs are endemic to Madagascar, and the indris are the only known singing species. While humans often consider themselves the only sopranos capable of producing complex songs, the indris demonstrate that other creatures can evolve comparable vocal adaptations.

The research also reveals that indris use slower songs with longer pauses to reunite after separation, illustrating the depth of their social communication.