Singing Lemur Uses Opera Techniques to Amplify Calls, Study Finds
Researchers discovered that Indri lemurs open their mouths wider on higher notes, a technique similar to that used by trained human opera singers.
The world's only known singing lemur species, the Indri, employs vocal techniques remarkably similar to those of trained opera singers to amplify their calls, according to a new study published in PLOS Computational Biology.
Researchers observed that Indri lemurs open their mouths wider when they attempt to hit higher notes. This deliberate adjustment of the vocal tract—encompassing the mouth, jaw, and tongue—helps match the frequency of the desired note, a process known as formant tuning. This technique amplifies the sound, allowing the lemurs' calls to travel further through their dense forest habitat in Madagascar.
This observed behavior is particularly surprising because formant tuning is a technique that human opera singers often train for years to master. Dr. Chiara De Gregorio from the University of Warwick, a co-author of the study, noted that before the invention of microphones, opera singers needed to project their voices to the back of large theaters. "Both opera singers and singing indris appear to use a configuration of the vocal tract that helps maximize the intensity of particular frequencies, making the sound more effective at a distance," she stated.
The research team analyzed 83 video recordings of 19 wild Indris using motion-tracking tools. This frame-by-frame analysis allowed them to map the lemurs' lip movements to the pitch of their songs, confirming the correlation between higher notes and wider mouth openings.
For Indris, singing is not merely an incidental behavior but a critical survival mechanism. These lemurs inhabit small family groups in Madagascar's rainforests and must defend large territories for resources. Approximately 90 percent of this territorial defense is achieved through singing rather than physical confrontation.
Every morning, Indri groups emit loud, far-carrying songs to announce their presence to neighboring groups and assert territorial claims. By employing these singing techniques, Indris can communicate effectively over long distances, reducing the need for physical patrols of their boundaries. Their calls have been recorded traveling up to 1.2 miles (two kilometers) through dense forest.
"What is fascinating is that a relatively simple adjustment of the vocal tract can have such an important ecological function," Dr. De Gregorio explained. "Sound travels much faster and farther than an animal could move through dense forest, so vocal communication provides an extremely efficient way of advertising and defending a territory."
The study also suggests that these findings could offer insights into the evolutionary origins of human musical abilities. Humans and lemurs share a common primate ancestor dating back approximately 74 million years. The similarities in their singing techniques are likely a result of convergent evolution—where different species independently arrive at similar solutions to similar problems.
"Our findings suggest that some of the mechanisms that make human singing effective may not be uniquely human inventions," Dr. De Gregorio said. "This does not mean that human singing evolved directly from indri singing, of course, but it shows that some of the underlying principles of effective vocal communication can evolve independently in different species facing similar communication challenges."