Brainwave experiments reveal that minke whales have ultrasonic hearing

EEG tests on two young baleen whales reveal they can hear sounds at higher frequencies than previously thought, leading researchers to explore how the ocean’s largest animals respond to noise from predators and humans. We are being forced to reconsider how we react.

“This is really groundbreaking research,” says Susan Parks of Syracuse University in New York, who was not involved in the new study. “Directly measuring hearing in wild baleen whales is something researchers in this field have been working on for decades…To my knowledge, this is the first successful test of this method in baleen whales. is.”

However, baleen whales are the largest animals on earth, and research methods such as temporarily restraining them for hearing tests are not easy. “Most baleen whales are too large for this approach to be effective,” said Dorian Hauser of the California-based nonprofit National Marine Mammal Foundation. So Hauser and his colleagues focused on a relatively small baleen species called the minke whale.

Researchers investigated the migratory routes of minke whales along the Norwegian coast and discovered a natural channel between the two islands, where they used mesh fencing and boats to capture the two whales, which are about 3 to 5 meters long. The whales were guided to an enclosure at the farm. Drop down net door. The researchers then used a roller system to pull up the net, keeping the teens partially submerged in the water.

For the hearing tests, the researchers were able to record brain wave signals by placing two gold-plated electrodes with silicone suction cups on each whale’s skin near its blowhole and dorsal fin. They measured how the whales’ brains responded to sounds played through underwater speakers for about 30 minutes in one whale and 90 minutes in the other.

These experiments have revealed that whales’ auditory brain stems respond to ultrasonic waves at frequencies as high as 45 to 90 kilohertz, which exceeds the ultrasonic waves that the human ear can detect. This is a much wider audible range than previously thought possible based on ear anatomy and speech production.

Oliver Boisseau of the UK-based nonprofit Marine Conservation Research said corralling and confining wild marine mammals is “quite controversial” because it can cause “significant stress” to the animals. ” states. But he said the discovery was “hugely important” for understanding how baleen whales evade predators such as killer whales, which use high-frequency echolocation clicks to hunt. .

Researchers should also reconsider how military sonar and commercial echo sounders used to map the ocean floor affect baleen whales, Boisseau said. “The more we study hearing in marine mammals, the more our initial assumptions seem to become confused,” he says.