A Cornell-led research team has developed an innovative method to estimate North Atlantic right whale numbers using underwater microphones and machine learning (ML), potentially offering a safer and more cost-effective way to monitor this critically endangered species.

The study, published Feb. 20 in Endangered Species Research, demonstrates how microphones combined with ML and traditional aerial survey methods can help track right whale populations in Cape Cod Bay, a crucial feeding ground where the whales gather each spring.

For effective conservation of endangered species, scientists need to know the whales’ location and how many of them there are. To get a handle on the number of right whales, researchers rely on costly and dangerous surveys by airplanes, or use sound recordings to identify their presence, or absence.

“Using sound recordings to monitor whale populations isn’t new,” said lead author Marissa Garcia of the Cornell Lab of Ornithology’s K. Lisa Yang Center for Conservation Bioacoustics, “but what makes our study unique is that we were able to take those recordings and go beyond getting information on the presence or absence of whales to getting an approximate number of whales in an area.”

The team – which included researchers from the Center for Coastal Studies, Harvard University, Oregon State University and Curtin University in Australia – set out an array of marine autonomous recording units (MARU) across Cape Cod Bay to capture right whale sounds. The MARUs used by the team were engineered and built by an in-house team of engineers at the Yang Center.

Following deployment of the MARUs, the team trained, validated and applied a deep-learning model that could automatically detect right whale sounds with 86% precision.

“By analyzing their distinctive upcall vocalizations, we can detect their presence continuously, day and night,” Garcia said. “This kind of round-the-clock monitoring that results from passive acoustic monitoring just isn’t possible with traditional aerial surveys, which can only happen in daylight hours and in good weather.”

The new methodology allowed scientists to obtain estimates of daily whale numbers in Cape Cod Bay. Garcia says there’s still some uncertainty in the counts that the team needs to address in future research, but the team is optimistic that monitoring whale vocalizations holds promise for estimating the abundance of right whales to aid in conservation and management efforts.

“By taking advantage of acoustic data along with airplane surveys, and by leveraging deep learning, we can greatly expand our understanding of animal behavior and really estimate the number of whales in this region at a fine time scale over a long time period," said co-author Irina Tolkova, a postdoctoral fellow at the Yang Center.

Having the ability to expand monitoring efforts across larger areas of the ocean will help scientists better assess the species’ population numbers across the full extent of its range. Garcia said right whales have been traditionally thought of as a conservation challenge in New England, but right whales are found all along the East Coast.

“Using passive acoustic data and deep-learning tools, we can expand the area we can safely monitor and keep track of this critically endangered species,” Garcia said.

The work comes at a critical time for North Atlantic right whales, whose population has declined to fewer than 370 individuals due to ship strikes, fishing gear entanglement and changing ocean conditions affecting their food sources.

“Accurate population estimates are essential for protecting this species,” Garcia said.

The researchers hope their methods can eventually be used to monitor other endangered or threatened whale species around the world. Said Garcia: “Our acoustic monitoring method adds a tool to our toolbox of possible ways to assess populations.”

This work was supported by funding from the Office of Naval Research, a National Science Foundation Graduate Research Fellowship, an Edward W. Rose Postdoctoral Fellowship, the Herchel Smith Undergraduate Science Research Program, the Harvard College Research Program and the Museum of Comparative Zoology Grants-in-Aid of Undergraduate Research.

Kathi Borgmann is communications manager for the Cornell Lab of Ornithology.