Birds are known for their beautiful melodious calls, but among mammals, no species besides humans have been known to use rhythm or songーuntil now. Researchers in Madagascar have documented lemurs using rhythm and even singing together in groups.

The 12-year study followed specifically the Indri indri species in the rainforest. The endangered lemurs were observed singing harmonized duets and choruses. Although their songs sound like high-pitched squeaks to the human ear, analyzed recordings of the group songs found that they had distinct rhythm, meaning they sang with intervals between sounds with exactly the same duration. In this case, they are singing in a 1:1 or doubled duration 1:2 rhythm.

The Indri indri lemur, also called the babakoto, is the largest living lemur species. Researchers from the University of Turin collected recordings from 39 animals living in 20 different groups for their study. The animals were even captured engaging in ritardando, the gradual slowing of rhythm within a piece of music.

The last common ancestor of the Indri indri and humans existed 77.5 million years ago, so the researchers believe their ability to produce song and rhythm evolved separately from humans, but their melodic tendencies could provide insights into humans’ use of music. Andrea Ravignani, one of the senior researchers, said, “Looking for musical features in other species allows us to build an ‘evolutionary tree’ of musical traits, and understand how rhythm capacities originated and evolved in humans.”

Source study: Current Biology – Categorical rhythms in a singing primate