Overview
- A peer-reviewed study published in PLOS Computational Biology on Monday, Sept. 21, 2026, reports that indri lemurs reliably widen their mouth opening as pitch rises.
- The result comes from frame-by-frame analysis of 83 field videos of 19 wild indris using synchronized audio and markerless motion-tracking to map lip and jaw position to vocal frequency.
- Scientists found the mouth-opening change tracked pitch note by note across individuals, which suggests the behavior is a species-level pattern rather than an individual quirk.
- Authors argue the movement likely boosts specific frequencies and helps songs carry long distances for territorial signals and group cohesion, though they cannot show the animals intend the adjustment and some video frames lacked usable landmarks.
- Researchers frame the similarity to trained human formant tuning as probable convergent evolution and note conservation concern because indris are declining, hard to keep in captivity, and depend on intact forest habitat.