Deploying a sound buoy into the ocean

Powered by Sound, Researchers Help Protect Animals Worldwide

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From birds and whales to elephants and gibbons, scientists at a Cornell-based center are using bioacoustics to spur conservation

By Lindsay Lennon

A haunting-but-enchanting duet of South Asian gibbons. The thunderous growl of an African forest elephant. A summery chirp of a common tree cricket. These are just a few of the auditory treats at the K. Lisa Yang Center for Conservation Bioacoustics.

From the depths of the seas to the treetops of wildlife-rich tropical rainforests, the Center collects and analyzes sound from environments around the globe to inform a range of conservation efforts.

“It’s like working in the zoo, except there are no animals,” quips the Center’s assistant director, Laurel Symes. “You walk up and down the hallway, and there are all these different sounds coming out of the different offices.”

The distinct call of Bornean white-bearded gibbons.

Symes’s favorite? Overall, “for pure beauty, gibbons”—but lately, she says, fish sounds have been blowing her mind.

“They make all kinds of trills and trains and thumps, and weird gurgling sounds and mating calls,” says Symes. “It’s like walking through a rainforest to drop a mic on a coral reef."

Based at the Lab of Ornithology, the Center and its 40 staffers use sound to learn about ecosystems—and, in turn, to help the species that inhabit them. It was renamed in 2021 in honor of K. Lisa Yang ’74, whose gift to the Center was the single largest in the Lab's history.

(A year later, Yang endowed a fellowship honoring renowned bioacoustics researcher Katy Boynton Payne ’59.)

As Symes explains: knowing what animals are in an area, when they’re active, and whether their population is declining, increasing, or stable can support better decision-making in managing habitats.

Underwater, on land, and high above ground, the Center performs acoustic monitoring across the globe to track endangered and threatened species. In Massachusetts Bay, for instance, for 15 years the Center has been using sound-detecting buoys to listen for endangered North Atlantic right whales.

Two researchers preparing an audio recording unit in a forest.
Researchers prepare tree-mounted units that will track insect populations in South America.

Since ship strikes are a leading cause of death for whales in the highly trafficked waterway, the buoys are equipped with transmitters that trigger alerts when whale sounds are present, allowing for real-time speed changes to avoid collisions.

Another project co-led by the Center comprises 2,000 recorders spread across the Sierra Nevada—where human-driven habitat changes led to a threatened population of California spotted owls being displaced by barred owls.

Snapping shrimp, toadfish, and spotted seatrout.

The research, which involved surveying an area roughly the size of Vermont, ultimately enabled the effective management of the barred owl population in the Sierra range.

“It was essentially a question of: ‘Do we watch the spotted owl go extinct, or do we do something?’” explains Connor Wood, leader of the Center’s ecology team for BirdNET, a research platform that detects and classifies animal sounds using machine learning.

It’s like working in a zoo, except there are no animals.

Assistant director Laurel Symes

Wood, who has been working on the Sierra Nevada project since he was a PhD student at the University of Wisconsin, Madison, in 2016, says the latest analysis of 2021’s data now shows a “negligible” presence of the barred owl in the area, and unofficial 2022 numbers indicate the same results.

“That shows us that these acoustic surveys work at a really big scale,” says Wood—noting that the recorders also pick up other animals in the area, like wolves and more than a hundred species of birds.

“With the power of these AI tools that we’ve developed at the Center, we can generate population data on all these other species,” he says, “and that’s exactly what we’re doing.”

Conservation bioacoustics research usually involves collecting massive quantities of sound recordings over extended periods; since animals are often hard to see, notes Symes, bioacoustic monitoring allows for long-term, around-the-clock observation.

In this vein, one of the Center’s main functions is to design and build recording equipment that can not only withstand natural environments, but also continuously record at low power consumption for long stretches of time.

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With the power of these AI tools that we’ve developed at the Center, we can generate population data on all these other species.

Researcher Connor Wood

“You can imagine putting your cell phone out, getting a recording for maybe six or eight hours, and then the battery dies,” says Symes. “Some of the equipment we’re building can record for months to years with off-the-shelf batteries.”

The Center builds some of its own equipment—like the SwiftOne recording unit, which can be mounted on a tree, and the Rockhopper, which goes thousands of meters under the sea.

Upcalls of a North Atlantic right whale.

It also designs software that processes the data, helps visualize and measure acoustic signals, and simplifies compression and storage. (The facility’s archives have a whopping 2 petabytes—more than 2 billion megabytes—of data.)

“If you have 40 or 50 units spread all over a national park for three months, it’s going to take a lifetime to listen through and see if an endangered species of bird is somewhere in that recording,” explains Symes.

“Machine learning has made a big difference for us in that respect. Even five years ago, this wasn’t possible; people were processing this data by hand.”

A mustached monkey eating fruit in a tree in Africa.
A mustached monkey, snacking in the Central African Republic. (Anahita Verahrami ’17)

More than a dozen scientists comprise the Center’s research arm, which not only deploys recording equipment all over the world, but works to analyze the data—and spur change as a result.

For example, the Elephant Listening Project—which seeks to conserve rare forest elephant populations in Central Africa—has been working to detect and prevent illegal gun hunting throughout the region’s national parks.

“It’s extremely hard to know where poachers are in these vast, dense rainforests,” explains the project’s lead, Daniela Hedwig. “We can monitor in very remote areas that are hard to access on a regular basis, and that’s how we can identify these previously undetected poaching spots.”

The thunderous sounds of an African forest elephant.

In partnership with on-the-ground conservation organizations like the World Wildlife Fund and Wildlife Conservation Society, the Project has also provided acoustic monitoring training and workshops for local research teams across Central Africa.

“They know poaching is happening—maybe they’ve found elephant carcasses or seen the gun cartridges—but they don’t have an exact understanding of where the poachers are going and when,” says Hedwig. “This is where acoustic monitoring can really help increase the certainty and accuracy of anti-poaching patrol efforts."

Since bioacoustics conservation is relatively niche, it has yet to be meaningfully practiced in many places that are ripe for it.

Elephants in a watering hole in Africa
Elephants in the Central African Republic. (Anahita Verahrami ’17)

To that end, Symes says, one of the most rewarding aspects of the Center’s work involves building connections with researchers around the world—from Southeast Asia to the Pantanal region of South America—who are working to conserve endangered species in their areas.

Says Symes: “Seeing these international conversations happening—and getting this technology into the hands of people who already know the conservation issues—has been super inspiring.”

Top: Deploying a sound-detecting buoy in Massachusetts Bay. All images provided unless otherwise indicated.

Published December 19, 2023


  1. Margo Berger, Class of 1957

    Fascinating! I recently visited the new Elephant Exhibit at
    the Museum of Natural History in New York City.

    There is a film among the diverse multi-media exhibits that
    refers to the use of biosonics to alert the Park Rangers to
    the location of poachers!

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