Bowhead whales are among the largest and longest-lived mammals in the world. They play a vital role in the marine ecosystems of the Arctic Ocean, yet relatively little is known about their foraging and diving behaviors.

Now, in a paper published in the journal Physical Review Research, a team of scientists from Japan, Greenland and Denmark have detected patterns in the whales' behavior that could offer clues into how they forage and socialize.

Associate Professor Evgeny A. Podolskiy at the Arctic Research Center, Hokkaido University, Professor Jonas Teilmann at the Department of Ecoscience, Aarhus University, and Professor Mads Peter Heide-Jørgensen at the Department of Birds and Mammals, Greenland Institute of Natural Resources, studied 144 days of diving records of 12 bowhead whales tagged in Disko Bay, West Greenland.

Because whale diving behavior can be seen as a chaotic, self-sustained oscillation that balances the need for food at depths with the need for oxygen at the surface, the researchers used a dynamical systems chaos approach to uncover patterns within the apparently disorderly collective behavior.

Their analysis detected a 24-hour cycle of diving during the spring, with the whales swimming deepest in the afternoon to track the daily movement of their prey towards the surface, a phenomenon known as the diel vertical migration.

"We find that foraging whales dive deeper during the daytime in spring, with this diving behavior being in apparent synchrony with their vertically migrating prey," said Heide-Jørgensen. "Until now, this hasn't been shown for spring, and remained contradictory for autumn."