Joanna Thompson, Hakai

Scientists observed two bowhead whales synchronizing dive schedules whenever they were within earshot of each other. Vicki Beaver, Alaska Fisheries Science Center, NOAA Fisheries, Marine Mammal Permit #14245

Researchers suspect the marine mammals may have been communicating across the vast distance

This article is from Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.

From January to May each year, Qeqertarsuaq Tunua, a large bay on Greenland’s west coast, teems with plankton. Baleen whales come to feast on the bounty, and in 2010, two bowhead whales entered the bay to gorge. As the pair came within roughly 60 miles of one another, they were visually out of range but could likely still hear one another. That’s when something extraordinary happened: They began to synchronize their dives. Researchers had never scientifically documented this behavior before, and the observation offers potential proof for a 53-year-old theory.

Baleen whales are often thought of as solitary—islands unto themselves. However, some scientists believe they travel in diffuse herds, communicating over hundreds of miles. Legendary biologist Roger Payne and oceanographer Douglas Webb first floated the concept of acoustic herd theory (or should it be heard theory?)  in 1971.

Payne, who helped discover and record humpback whale song a few years prior, was struck by the fact that many toothed cetaceans such as killer whales and dolphins are highly social and move together in tight-knit family groups. These bands provide safety from predators and allow the animals to raise their young communally. Payne speculated that the larger baleen whales might travel in groups, too, but on a broader geographic scale. And perhaps the behemoths signaled acoustically to keep in touch across vast distances.

Webb and Payne’s original paper on acoustic herd theory demonstrated that fin whale vocalizations—low-frequency sounds that carry long distances—could theoretically travel an astonishing 430 miles in certain areas of the ocean. However, it’s been easier to show that a whale is making a call than to prove the recipient is a fellow cetacean hundreds of miles away, says Susan Parks, a behavioral ecologist at Syracuse University in New York who studies animal acoustics.

For over 50 years, researchers have shared compelling anecdotes about baleen whales seemingly coordinating behavior over long distances, but the stories have remained just that—stories. It took a multidisciplinary research team studying bowhead diving behavior to stumble on evidence for acoustic herd theory. […]

More: How Did Two Bowhead Whales That Were 60 Miles Apart Sync Their Diving?