Musical lemurs mostly synchronize with their choirmates, but some go solo.
It might not be music to your ears, but it is the song of the indri — a critically endangered lemur from Madagascar and one of the only species of singing primate in the world.
The indri chorus, consisting of a series of loud howling cries, can be heard many times each day and from several kilometers away. Researchers working in the eastern rainforests of Madagascar wanted to know more about the musical lemurs’ sense of timing and pitch, so they recorded 496 indri songs over a period of 30 months.
Group members carefully coordinate their singing, according to a study now published in Frontiers in Neuroscience. As soon as one indri starts to sing, most other group members chime in. Indris also tend to synchronize their notes and match each other’s rhythms, the researchers found.
"The chorus songs of the indri start with roars that probably serve as attention-getter for the other singers and continue with modulated notes of that are often grouped into phrases. In these phrases the indris give a high-frequency note at the beginning, and then the following ones descend gradually in frequency," said lead author Marco Gamba, a Senior Researcher at the University of Turin, Italy, in a press release.
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Though most of the singing did not overlap, the indris reliably co-sang certain parts of their song with other group members. Synchronized singing produces louder songs, which may deter other indris from trespassing on a group’s territory.
The younger, lower-ranking males, on the other hand, were more often heard singing out of synch with the rest of the chorus. Alternating their notes with those sung by the dominant male and female of the group may be a way for the subordinate males to emphasize their individual contributions to the song.
“This lets them advertise their fighting ability to members of other groups and signal their individuality to potential sexual partners," suggests co-author Giovanna Bonadonna.
Similar to humans, the researchers also found that indri males and females sang at different pitches. But in their case, it was the males who hit higher notes more often than the females.
According to the authors, “The indris are good candidates for further investigations of the evolution of typical speech features because the turn-taking between individuals, the constant exchange of short vocal units, and the variable degree of overlap are shared trait of modern human communication.”
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