New Bay Area Research Reveals the Secret Lives of Sperm Whales

Sightings of sperm whales are rare in Monterey Bay. But that doesn’t mean they aren’t nearby, deep under the surface of the ocean.

Scientists at the Monterey Bay Aquarium Research Institute analyzed a trove of acoustic data recorded with a deep-sea hydrophone there and discovered that these endangered species are more common than they previously thought.

“To see a sperm whale or its unique sideways spout, we must be nearby on a boat. But underwater, we can hear the unique sound of a sperm whale’s echolocation from a hundred miles away,” explained John Ryan, a biological oceanographer who led MBARI’s ocean soundscape team and coauthored the recent study.

Sperm whales are the loudest animals on the planet. That might be a little surprising if you are just listening to the recordings, clicks that sound like a combination of Morse code and popping popcorn.

What do those sounds tell us about their behavior and ecosystems?

Ryan’s group analyzed millions of whale sounds recorded over seven years in the Monterey Bay National Marine Sanctuary, working along with collaborators from the Naval Postgraduate School and the University of Washington’s Center for Ecosystem Sentinels.

The interval between echolocation clicks sperm whales produce can indicate the age and sex of individual whales. These sounds can also reveal whether the whales are actively hunting or have successfully captured their meal.

Researchers also learned that these animals are more present in Monterey Bay in the winter, providing strong evidence that sperm whales migrate seasonally in the Northeast Pacific Ocean.
Scientists used to think the opposite, based on research from further north in the Gulf of Alaska that found a summer peak in whale vocalizations.

These patterns suggest seasonal migrations previously unrecognized in sperm whales that likely align with the shifts of the North Pacific Transition Zone — a biologically rich region where cooler and warmer ocean waters meet.

“What we’re hearing actually is a really unique seasonal migration in this top predator of the deep sea,” said William Oestreich, MBARI Postdoctoral Fellow, who led the research.

These findings reinforce the idea that deep-sea environments experience seasonal changes, with top predators like sperm whales playing a critical role in maintaining the health of oceanic ecosystems.

Sperm whales are the largest-toothed predators with the biggest brains in the animal kingdom. They can grow up to 52 feet in length and weigh up to 45 tons. They remain largely enigmatic despite their size. “These animals are just very cryptic. They are very deep-diving animals,” Oestreich said.

They dive hundreds or even thousands of meters below the ocean’s surface to hunt for squid and fish, using echolocation to find prey in the darkness of the deep sea. Their distinctive clicks provide scientists with valuable information about their behaviors.

“Animal sounds contain such rich information about who these animals are and what they’re doing. It’s just up to us as researchers to decipher that meaning,” Oestreich said.

Through acoustic data analysis, MBARI researchers aim to support conservation efforts for sperm whales and other endangered species. This research provides crucial insights for decision-makers working to protect these vital marine environments and their inhabitants.

“There’s a lot of value here in just understanding the lives of these animals a little bit deeper for the pure fascination and appreciation of it, but also hopefully so we can better protect the ecosystem that they’re dependent on,” Oestreich said.