Frame-by-Frame: Researchers Show How the Indri Sings

A PLOS Computational Biology study used markerless motion tracking on 83 videos of 19 wild indris to link mouth opening directly to pitch.

Multiple outlets in this pack, including KVRR and Nonstop Local, report that a new study published in PLOS Computational Biology offers the first direct evidence that wild indris coordinate their mouth opening with the frequency of their songs. The indri, found only in Madagascar's rainforests, is the world's only known singing lemur, and the research suggests it opens its mouth wider on higher notes much as a trained soprano does when projecting through a concert hall.

According to the pack's syndicated Talker report, the research team analyzed 83 video recordings of 19 wild indris, combining field audio with markerless motion-tracking technology. They tracked upper and lower lip position frame by frame, comparing changes in mouth opening with changes in vocal frequency, and found the lemurs opened their mouths wider to project higher-pitched vocalizations through the forest. First author Filippo Carugati of the University of Turin said the method let the team study how the face and mouth move while an animal sings, something he says you simply cannot capture by listening to audio alone.

Corresponding author Chiara De Gregorio, an honorary research fellow at the University of Warwick, told the pack's sources that every time an indri's pitch rose, the team could see its mouth opening wider, frame by frame. She described it as the kind of fine-tuned coordination between voice and body usually associated with trained human singers, not a lemur singing from the forest canopy. Outlets carrying the report frame this as a striking parallel to opera technique emerging in a wet-nosed primate.

The reports explain that human singers are trained to widen their mouths as pitch rises, aligning the resonant frequencies of the vocal tract with the harmonics of the voice and amplifying the sound — a process known as formant tuning. For an animal communicating through dense forest, the outlets say this could make the difference between a song that carries and one that does not. Indris produce complex, haunting songs that carry across vast distances, strengthening bonds within their social group and warning neighboring groups to keep their distance.

According to the Talker report carried by the Killeen Daily Herald, first author Filippo Carugati noted that humans and indris last shared a common ancestor around 74 million years ago, meaning similarities in vocal production between the two species are likely the result of convergent evolution — the same solution arrived at independently across deep evolutionary time.

The outlets syndicating this report, all drawing on Talker's Stephen Beech, present the findings as an opening move rather than a conclusion: markerless pose estimation applied to wild footage allowed the team to connect physical movements directly to changes in pitch, and the pack's coverage suggests this method could now be applied to other singing animals. For singing enthusiasts, the story lands as a reminder that the mechanics taught in vocal studios — opening up on high notes to let the sound ring — appear to have evolved independently in a lemur. Yahoo's video version frames the takeaway the same way: an opera trick, discovered in Madagascar's canopy.