With their unusually long arms, gibbons are the masters of the treetops. But these rainforest dwellers also have extraordinary voices which they use to defend their territory.
The gibbon is a lesser ape that lives in Southeast Asia. Its long forearm allows it to swing almost effortlessly from tree to tree. But have you ever heard a gibbon sing? They begin each day with a burst of music, singing their spectacular songs for a good 30 minutes. The trilling call can be heard kilometres away.
Gibbons sing to mark out their territory
It turns out that gibbons employ the same techniques to make music that human soprano singers use when they sing opera. Primatologists at the University of Kyoto in Japan placed a young female gibbon in a chamber and let her sing. They recorded about 20 calls in this normal atmosphere. Then, they added helium to the chamber’s atmosphere. This gas is less dense than regular air. Just like humans, gibbons begin to make high-pitched squeaking sounds because the gas pushes the resonance frequencies of the vocal tract upward.
Similar vocal tracts
The sound of a gibbon's call originates in the larynx, just like in humans. It is separate from the vocal tools used to modify it, as is the case with human beings. This means the gibbon used in the Japanese study was able to consciously regulating the sounds she was making.
The gibbon heard her voice making strange sounds as the helium was added to her chamber, so she modified the shape of her vocal tract – the larynx – as well as the oral and naval cavities. Even for an expert opera singing human being, it would take years of study to master and manipulate the voice this way.
The study offers new insight into the evolution of gibbons and proves that the physiological basis of human language is not as unique as previously assumed.