Gorillas beating their chests, chimpanzees pant-hooting, elephants rumbling—and poachers firing assault rifles—these are some of the more than a million hours of sounds recorded by a grid of 50 microphones in the Congolese rainforest since 2017.
The massive acoustic monitoring effort covers about 480 square miles in the Republic of Congo’s Nouabalé-Ndoki National Park—an area about the size of Los Angeles. It’s part of Cornell University’s Elephant Listening Project, established in 1999 to detect communication among forest elephants and pinpoint poaching activity. The project has used acoustic methods to “estimate elephant populations, impacts of oil exploration and logging, and to quantify illegal gun-hunting in protected areas,” according to its website.
“For years I’ve been trying to get these sounds that we’re recording more accessible to other people,” says Peter Wrege, behavioral ecologist and project director. That’s now come to pass: The myriad forest sounds are now available to researchers worldwide via the cloud platform Amazon Web Services.
Listening for poaching activity allows anti-poaching teams to assess the effectiveness of their strategies, Wrege says. For example, during a three-month ranger training period in early 2018 when patrols were reduced while rangers were undergoing training, recordings of gunshots spiked. The audio also showed that poaching was occurring deeper in the park than expected, leading rangers to adjust their patrolling patterns. Wrege says he was surprised to learn that poaching didn’t increase during the coronavirus pandemic.
“A lot of money” goes into anti-poaching patrolling in many countries, he says, but is that actually reducing crime? In Congo, the audio recordings provide confirmation that as anti-poaching patrols were intensified during 2018, hunting activity decreased.
Using acoustic monitoring to track poaching is a burgeoning field, and sharing recordings is a new and growing practice. Topher White, an engineer and National Geographic Explorer, founded his bioacoustic monitoring company, Rainforest Connection, in 2014 to monitor illegal logging, detect poaching activity, and create a digital library of rainforest audio that includes Wrege’s Congo recordings.
Using recycled cell phones, White’s team detects sounds from trucks, motorcycles, chain saws, and gunshots in real time in 20 countries. Park rangers, scientists, anyone, for that matter, can access the recordings through the company’s website and app.
Marconi Campos, one of Rainforest Connection’s biologists, says it’s common to hear researchers “bragging about how many data they had in their hard drive.” One of the Rainforest Connection’s goals is to end data hoarding by encouraging scientists to upload their recordings to its platform.
“It’s a real chore because there’s a culture around not sharing,” White says. “That’s what we’re trying to change, because there’s so much amazing stuff out there.”
Wrege’s audio “was like a goldmine,” he says. His team of scientists and interns had been scouring the internet for recordings of elephant infrasound rumbles, inaudible to humans, that the animals sometimes use to communicate, when they came across Wrege’s recordings. Picking out those sounds was difficult—“it’s not even a needle in a haystack, it’s like an invisible hair,” White says—but after they identified one example, they were able to scan the database for hundreds of similar sounds.
“Fantastic opportunities” for further research based on the Congo audio and other recordings collected around the world exist, Wrege says. Researchers might use the trove to study other species—insects, frogs, birds, gorillas, chimpanzees. “It’s all on there in these recordings,” he says. He also envisions a museum collection of bird calls, akin to an exhibit displaying bird skeletons. “It’s a historical record.”
“It’s a really exciting moment for bioacoustics,” White agrees. “There’s entire worlds of animal behavior and animal interaction,” he says, “that computers will be able to pick out.” Worlds that until now have been invisible or inaudible to us. With climate change reshaping our planet, “this is possibly the most important moment for people to be gathering extraordinary multitudes of data with as great detail as possible … It’ll all be gone if we don’t capture it now.”