First successful test of wild minke whales reveals they have ultrasonic hearing

23 Nov 2024, 16:00 by Bob Yirka

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Animal handling procedures. (A) Minke whale undergoing an AEP hearing test. The non-inverting electrode and reference electrode are caudal of the blowhole and rostral of the dorsal fin, respectively. The attending veterinarian (C.A. Harms) is pictured collecting a blood sample from the dorsal fin in this image. (B) Post-release view of the dorsal fin–mounted satellite tag. Credit: Science (2024). DOI: 10.1126/science.ado7580

A team of marine biologists from Norway, the U.S. and Denmark has conducted the first hearing test of a live baleen whale. For their study published in the journal Science, the group corralled a pair of wild minke whales and recorded their brain waves.

Concerned about how human-produced ocean noises may impact the creatures that live in the sea, marine scientists want to learn more about the animals' hearing capabilities. In this new study, the research team devised a means for testing the hearing of two wild baleen whales by recording their brain waves as they listened to recorded sounds.

The research team chose the minke whales as test subjects because of their relatively small size compared to other whales. To capture their brain waves, they studied their swimming routes through a narrow channel between two islands off the coast of Norway. Next, they placed netted barriers near the area that directed the whales to a small enclosure.

Once they had trapped two whales, they pulled up a net below them, bringing them to the surface. This allowed the researchers to affix electrodes to their heads. The team used the electrodes to record the whales' brain waves as they responded to sounds played from nearby speakers. One of the whales was tested for a half-hour, the other an hour and a half. The researchers then released the whales back into the wild.

The brain wave recordings mark the first such successful test of their kind. The research team found that the whales responded to most sounds as had been predicted based on prior research that studied the ear structures of dead whales. They also discovered something unexpected—the whales were capable of hearing ultrasonic sounds, a finding that suggests all baleen whales may be able to hear such sounds.

This means that marine scientists will have to review prior work attempting to understand how whales respond to sonar, underwater echo sounders and other sounds and noises made by ships and seacraft. The finding could also lead to new research on how baleen whales protect themselves from killer whales.

More information: Dorian S. Houser et al, Direct hearing measurements in a baleen whale suggest ultrasonic sensitivity, Science (2024). DOI: 10.1126/science.ado7580

Journal information: Science