Scientists have captured a rare view of one of the ocean’s most elusive whales – without ever laying eyes on it. By listening to the sounds beaked whales produce as they hunt in the deep, researchers have reconstructed a three-dimensional portrait of their movements beneath the surface of the Gulf of Mexico.

In a groundbreaking development, the study delivers the first detailed description of the deep-diving behaviour of a Gervais’ beaked whale  (Mesoplodon europaeus) anywhere in the world. Relying solely on passive acoustic data, the work has opened a rare window into how this little-known species dives and forages in the deep ocean.

Given the depths as which they primarily inhabit and surfacing only briefly and somewhat unpredictably, beaked whales are among the most difficult marine mammals to study. Traditional visual surveys and animal-borne tags offer limited opportunities to observe them.

Instead, the research team turned to passive acoustics: underwater listening systems that detect the species-specific echolocation clicks whales emit while hunting. These acoustic signatures allowed scientists to follow the animals’ movements during deep foraging dives, providing a scalable and non-invasive approach to studying life in the deep sea – data that are increasingly vital for conservation and management.

“These findings come at a critical time for beaked whales in this heavily industrialised region,” said Héloïse Frouin-Mouy, Ph.D., lead author of the study and a bioacoustics scientist at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science’s Cooperative Institute for Marine and Atmospheric Studies.

“There is an urgent need for reliable data on the populations and behaviour of these whales, which are believed to be in decline.”

The urgency is underscored by earlier research suggesting that beaked whale populations in the Gulf of Mexico may have fallen by as much as 83% since the 2010 Deepwater Horizon oil spill. Despite this apparent decline, fundamental questions about the animals’ behaviour, habitat use, and vulnerability to human activity have remained unanswered.

To address these gaps, researchers deployed specialised underwater listening systems on the seafloor off the coast of Louisiana, at depths of approximately 1,100 metres (3,600 feet). Two High-Frequency Acoustic Recording Packages (HARPs), each equipped with multiple time-synchronised sensors, recorded echolocation clicks from beaked whales during 50 deep foraging dives. By measuring minute differences in the time it took each click to reach individual sensors, the team could determine the direction of the sound.

It was when data from both systems were combined, the whales’ three-dimensional underwater trajectories emerged.

Using this approach, the researchers tracked the dive behaviour of three species – goose-beaked, Gervais’, and Blainville’s beaked whales. Goose-beaked whales were detected for longer periods and were found to conduct deeper foraging dives than the other species, often descending to near the seafloor. The findings reveal striking differences in how closely related species use the deep-ocean environment.

The research was carried out as part of the LISTEN (Long-term Investigations into Soundscapes, Trends, Ecosystems, and Noise) project, a long-running collaboration led by NOAA’s Southeast Fisheries Science Center, the Scripps Institution of Oceanography at the University of California San Diego, and multiple partners.

Titled “Beaked whale dive behaviour and acoustic detection range off Louisiana using three-dimensional acoustic tracking,” the study was published on February 4, 2026, in PLOS One.

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