What inspired you to study marine mammals?
MC: Ever since my childhood growing up in Spain, I’ve been interested in animals. Once a chair went missing in our house, and my parents found it on the roof because I had been sitting up there, observing cats moving across the houses.
I’ve been especially interested in how animals live in the mysterious ocean environment, which led me to study marine biology, and eventually bioacoustics — the study of animal sounds. I was drawn to whales and dolphins in particular because of their curiosity.
Tell us how whales and dolphins use sound.
MC: We humans use our eyes to scope out the world around us. For marine mammals, the dominant sense is sound, which makes sense because underwater visibility is often limited.
Because water is denser than air, sound travels more easily and farther in water. If I shout into the air, the sound becomes fainter the farther it travels. But in the water, that fade is much milder. Sounds can travel hundreds of miles away. Dolphins and whales use sound signals to socialize and to find other animals. Dolphins in particular can construct a picture of their environment using only sound — something called echolocation.
How do scientists use bioacoustics to pick up marine mammals’ sounds?
MC: For scientists, sound is a handy signal to learn where these animals are and what they’re doing. Often we use microphones anchored to the seafloor to record sound waves. Back on land we analyze these signals for certain whistles, calls, and echolocation clicks. From these sounds, we can tell where and when the whales and dolphins are detected, what they’re doing, and whether they’re staying or just passing through. Or, if we hear young animals, we know it’s a nursery. My work has focused describing these signals and converting them into data.
Most recently, you studied North Atlantic right whales with NOAA. Why these whales?
MC: NOAA’s mission has historically involved protecting marine life and minimizing their risk of extinction. Because we estimate there are only around 370 North Atlantic right whales left, they have been a top priority. NOAA has done a lot of work to understand these whales’ behavior and how they use their habitat. Research revealed two main threats to their survival: entanglement in fishing gear and strikes from vessels. And the latter has a lot to do with noise pollution.
Can you explain how noise pollution impacts whales?
MC: If you’re crossing a highway at 3 a.m. with your eyes closed, you know when a car is coming and what direction it’s coming from because the road is so quiet. But if it’s rush hour, you can’t easily identify a gap in traffic to cross because of all the noise. That’s what’s happening in the oceans for right whales — because there is so much traffic noise, they can’t locate where a particular ship is or which way it’s going. By the time the vessel is right there, it’s too close to avoid and they get hit.
In 2001, I was working at a research station nearby the summer breeding ground for North Atlantic right whales. When the tragedy of September 11 happened, shipping and air traffic stopped and most of the North Atlantic no longer had this chronic noise pollution. With ambient noise at preindustrial volumes, the whales’ cortisol levels — which reflect their stress levels — were way down. They enjoyed a quiet environment for the first time in their lives.
This was the first study addressing the effects of chronic ship noise exposure on whales, and thanks to more recent work in this field, NOAA is developing a strategy to minimize the acute, chronic, and cumulative impacts of noise on marine animals.
You worked with colleagues at NOAA to track the movements of whales using AI. Tell us more about this effort.
MC: Analyzing hours of sound recordings is tedious and costly, so we collaborated with the Microsoft AI for Good Lab to use machine learning to process sound recordings for a beluga whale program in Alaska. The AI models increased our accuracy and saved us up to 70% of the time it takes to analyze the recordings.
A few years ago, Congress asked NOAA to expand its acoustic monitoring efforts for North Atlantic right whales, and I was selected to lead this effort in the Southeast. The expansion plan aimed to more than triple the number of sensors collecting acoustic data on right whales from North Carolina to Florida, using AI to support these efforts. Just last year, I relocated to Florida for the project.
Unfortunately, when my role changed, it meant I was under a temporary “probationary” status, and earlier this year, the Trump administration fired most probationary employees across the government, including me.
How will the NOAA cuts impact this project and others?
MC: Working on a team of three, I was the project leader and the only person with AI experience. Now my former colleagues are struggling to stay on schedule without the planned AI assistance. The cuts at NOAA will have far-reaching consequences, from reducing the chance of survival for right whales, to weakening the agency’s ability to issue hurricane and tsunami alerts.
How does tracking whales help the public?
MC: Fishers and the shipping industry do not want to harm whales. They also don’t want to damage their vessels or expensive gear. Using acoustic monitoring, we’ve seen that when whales went to new areas to feed — places where vessel traffic and fisheries weren’t regulated — deaths went up. Monitoring also helps NOAA fine-tune regulations to avoid closing fisheries or limiting vessel speed in places where whales aren’t present. Thanks to this information, NOAA can more precisely target protection measures in a way that benefits everyone. It’s a win-win for whales and people.
Dr. Manuel (“Manolo”) Castellote is a marine scientist who has spent his career listening to the oceans — especially the whales and dolphins that call them home. At the beginning of his career, “bioacoustics” was still an emerging field. Twenty-five years later, Castellote and his colleagues have learned how to detect where whales and dolphins gather — and how to use artificial intelligence (AI) to help protect them. Castellote worked with the U.S. National Oceanic and Atmospheric Administration (NOAA) for 15 years, prior to being let go during the federal government’s mass layoffs earlier this year.
