An AI listening network estimated how many singing indri lemur families live in a Madagascar forest, and it landed close to the real number

University of Turin researchers hung 26 recorders in Madagascar’s Maromizaha forest and used an AI model to pick out the songs of the indri, the world’s largest lemur. Their peer-reviewed estimate of 5.55 indri groups per square kilometer came close to the known 6.17, a promising way to count a critically endangered species without disturbing it.

Indri fill the rainforests of eastern Madagascar with loud, musical duets. These black-and-white animals are the world’s largest lemurs and the only lemurs that sing, using their songs to claim territory from rival groups. They are also critically endangered, and every attempt to keep them in captivity has failed, so saving them means protecting the wild ones. That starts with knowing how many are left, which is hard to work out in steep, tangled forest.

The clever bit

Let the lemurs announce themselves. A University of Turin team strapped 26 recorders to trees across the Maromizaha New Protected Area and had them capture 10 minutes of every half hour for about 13 months. A neural network trained on indri songs combed the morning audio and flagged 5,395 songs. The team then borrowed a counting method first used for animals in the ocean: combine how many songs the recorders catch, how often a group sings and how likely a song is to reach a recorder, and out comes an estimate of how many groups live nearby.

Maromizaha made a fair test because researchers already knew the answer. Scientists have followed habituated indri groups there for 15 years, and the real density is 6.17 groups per square kilometer. The recordings put it at 5.55, with the true figure inside the estimate’s range. The peer-reviewed paper, published October 9 in Conservation Science and Practice, calls that strong agreement.

Every song we detect is a data point that could guide where conservation efforts need to go next.

— Valeria Ferrario, postdoctoral fellow, University of Turin, via nationalgeographic.com

Hooray

Conservation teams can count a critically endangered lemur by listening. There are no loudspeakers playing calls that can change indri behavior, and far less time hiking survey lines in bad weather. The authors say the setup needs only a network of recorders, about one per square kilometer, which keeps costs within reach for groups with small budgets.

What comes next

The team hopes to use the method across the indri’s whole range in Madagascar. National Geographic reports that the University of Turin and partners also support GERP, the local group that manages Maromizaha and helps residents grow native trees to replant cleared forest.

How solid is it?

Promising: Results measured in a study or bounded trial. Limitations and wider testing still matter.

Peer-reviewed, open-access paper in Conservation Science and Practice (published October 9, 2026) by Ferrario and colleagues at the University of Turin, validated against a forest where the real indri group density was already known from 15 years of fieldwork. Independently reported by National Geographic on October 22, 2026. Tested in one forest so far.

See for yourself.

Selected for Oct 24, 2026. Reviewed Oct 24, 2026, 5:49 AM MT. Source dates may be earlier than this edition.