When an opera singer stands on stage and belts out a high note, they usually open their mouths wider, letting the song ring out. It turns out that trained opera singers aren’t the only ones to do so.
Deep in the rainforests of Madagascar, the wild indris, also called the ‘singing lemur,’ are known to belt out high notes from the canopy, and they use the same method as opera singers, according to a new study in PLOS Computational Biology.
"Every time the pitch of an indri's song rose, we could see its mouth opening wider, frame by frame," Chiara De Gregorio, corresponding author and Honorary Research Fellow at the University of Warwick, said in a press release. "It's the kind of fine-tuned coordination between voice and body that we usually associate with trained human singers, not with a lemur singing from the forest canopy."
What Are Indri the Singing Lemurs?
The rainforests can be full of sounds. From chirping birds to croaking frogs, there is noise all around. But perhaps nothing sounds quite as haunting and unique as the high-pitched call of the Indri, the singing lemur. Madagascar is home to many lemur species, each with its own unique traits. For the indri, it’s “singing,” and their vocal techniques are similar to those of human singers, especially opera sopranos.
Explore All OptionsThe high-pitched sound is similar to someone slowly letting air out of a balloon or to a whale call. It’s loud enough to pierce the thick rainforest canopy. According to Wildlife Madagascar, the calls can be heard through the forest from over a mile away and can last about 3 minutes.
These lemurs use these vocalizations to communicate with each other, whether to warn of danger or claim territory. In some cases, it’s to find one another amongst the thick foliage. According to reports from Reuters, the lemurs calling back and forth is similar to people playing a game of Marco Polo.
Lifting Their Voices
For the study, researchers from the University of Warwick analyzed 83 video recordings of 19 wild indris. They then combined audio with markerless motion-tracking technology to track how upper- and lower-lip position changed from frame to frame. By comparing changes in mouth opening with changes in vocal frequency, the team noticed that the lemurs opened their mouths wider while projecting high-pitched calls.
Monitoring the mouth movements of an indri
(Image Credit: Filippo Carugati)
“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 Filippo Carugati of the University of Turin in the press release. "It let us study how the face and mouth move while an animal is singing, almost frame by frame, and connect those movements directly to changes in pitch. That's something you simply can't capture by listening to the audio alone."
Human singers are trained to do the same thing while singing high notes, according to the study, a technique known as formant tuning. A wider mouth helps align the vocal tract's resonant frequencies with the voice’s harmonics and amplifies the sound.
It appears that formant tuning may help these lemurs project their calls further out, instead of them getting lost in the leaves.
The study also notes that humans and the wild indris shared a common ancestor about 74 million years ago. The research team believes this shared vocal technique could result from convergent evolution, a trait each species developed independently over time.
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in PLOS Computational Biology: Dynamics of jaw kinematics and fundamental frequency suggest vocal tract tuning in the indris’ song
- This article references information from Wildlife Madagascar: Indri indri
- This article references information from Reuters: Singing lemurs may use a soprano-like trick to project songs
