Singing Lemur Copies Opera Singers By Opening Its Mouth Wider For High Notes

The indri, the world’s only known singing lemur, appears to use a vocal technique remarkably similar to trained human opera singers when reaching higher notes.

Researchers found that the higher the pitch of an indri’s song, the wider it opens its mouth. The discovery provides the first direct evidence that wild indris coordinate mouth opening with the frequency of their songs.

Indris live only in the rainforests of Madagascar, where their complex songs carry across long distances, strengthening social bonds and warning neighboring groups to keep their distance.

Human singers widen their mouths as pitch rises, a process known as formant tuning that helps amplify vocal harmonics. Researchers suggest indris may use a similar technique to help their songs travel through dense forest.

“Every time the pitch of an indri’s song rose, we could see its mouth opening wider, frame by frame,” said Dr Chiara De Gregorio, corresponding author and Honorary Research Fellow at the University of Warwick.

The team analyzed 83 video recordings of 19 wild indris using field audio and markerless motion-tracking technology. They tracked upper and lower lip movements frame by frame and compared mouth opening with changes in vocal frequency.

“Applying markerless pose estimation to footage recorded in the wild allowed us to look not just at the sounds indris make, but at the physical movements behind them,” said first author Dr Filippo Carugati of the University of Turin.

Humans and indris last shared a common ancestor approximately 74 million years ago. Researchers say the vocal similarities are likely an example of convergent evolution.