Singing lemurs reveal a vocal trick familiar to opera singers

Scientists have found that Madagascar’s singing lemurs open their mouths wider as their notes rise, evidence of a vocal technique similar to one used by opera singers.

For the study, published in PLOS Computational Biology, researchers used software to track the animals’ lips in videos recorded in the wild. After unusable frames were removed, footage of 12 indris showed a consistent link between mouth opening and pitch in both males and females. The method required no contact with the animals.

To explore what that movement does, the researchers built acoustic models using casts of indri skulls. The models suggested that a wider mouth shifts the frequencies naturally amplified by the vocal tract towards the pitch being sung. Sopranos use a similar adjustment to help high notes carry.

That could be useful in eastern Madagascar’s dense rainforests. Indris, the only lemur species known to sing, use their songs to defend territory and strengthen bonds within family groups.

The recordings cannot establish whether the lemurs adjust their mouths deliberately, and models are not direct measurements of a living animal’s throat. Even so, the findings suggest that very distant branches of the primate family have independently arrived at a similar way to make their voices carry.