Listening with AudioMoth

An AudioMoth is a small, open-source sound recorder made by Open Acoustic Devices. It fits in your palm, runs on three AA batteries and records onto a memory card. One costs about $100. Tie it to a tree and it will listen for weeks: birds at dawn, frogs after rain, insects at night, and also boats, chainsaws and people.

In a short film made with Oceanus Conservation in the Philippines, David Dao of GainForest describes it like a radio. Every animal has its own channel, and the recorder picks them all up: "the Spotify playlist of nature." You only need to hear an animal, so sound catches species that cameras and walking surveys miss. In India's Sundarban mangroves, a team from Darukaa Earth put out three recorders, collected about sixteen hours of sound, and identified 25 to 30 species in it.

The hardware is the easy part. In Cagwait, before anything went up a tree, Oceanus, local fisherfolk and GainForest agreed on a question: is there more life in restored mangroves than in unrestored ones? That question decided where the recorders went. Some of the sites had been fishponds before they were replanted. Then came the practical choices. Recordings at 48 kHz, enough for birds, bats and insects. One minute of recording, then four minutes of sleep, all day, so the batteries and card would last about two weeks. A waterproof case, a camouflage cover, thin rope, and a spot high enough to stay dry at high tide and hard for passers-by to notice. When the tide came in before the last sites were done, a fisherwoman took the team the rest of the way on her bamboo raft.

In 2026, near Manaus, the children at Arte & Escola na Floresta took over. They had watched the adults set up the equipment, and then they chose a tree on the far bank of the river and swam out to tie the recorder to it themselves. Democratising technology turned out to mean something simple. The people who live there decided where to listen.

Once the cards come back, the recordings need a home and a set of rules. Partners now upload them to Soundscapes on the GainForest app, which keeps each file linked to the recorder that made it, the place, the time and the person who put it out. Teams can mark sounds on a spectrogram, the picture of a recording, and label what they hear with local experts or with school classes.

Two questions decide whose data this is. First, who may listen? A recorder near a village hears voices, arguments and the routes people walk. As one of our community leads put it to new grantees, recordings can reveal "where people live, where people work, where people gather." Everything uploaded to the GainForest app is public, so the community's data council decides what goes online before anything is uploaded.

Second, who pays for the walking? Setting recorders, going back for the cards and uploading the files takes days. Most of our partners in Manaus have done it so far without pay, because they care about the work. That cannot last. In GainForest's Conservation Data Income model, the community's council sets a price per minute of recording, and the person who did the work is paid. Lesson 12 looks at how that money actually reaches people.