Scientists applied chaos theory to the movements of iconic Arctic whales and discovered a 24-hour dive cycle and long-range synchronization (~100 km).

A recent study has revealed complex bowhead whale behavioral patterns that show a 24-hour deep dive cycle synchronized with the movement of prey in the spring. Scientists discovered this pattern using chaos theory and observed two whales coordinating their long-distance dives, suggesting a complex social structure and possible acoustic communication between these arctic giants.

Bowhead whales are one of the largest and longest-lived mammals on Earth. They play a vital role in the marine ecosystems of the Arctic Ocean, but relatively little is known about their foraging and diving behavior. In a paper to be published in a journal Physical Examination ResearchA team of scientists from Japan, Greenland and Denmark has discovered behavioral patterns in whales that could provide clues about how they forage and communicate.

Associate Professor Yevhen A. Podolsky of the Arctic Research Center
Professor Jonas Teilmann, Department of Ecology, Hokkaido University
Professor Mads Peter Heide-Jørgensen from Aarhus University and Professor Mads Peter Heide-Jørgensen from the Department of Birds and Mammals at the Greenland Natural Resources Institute examined 144 days of dive records from 12 bowhead whales seen in Disko Bay, West Greenland. Since whale diving behavior can be viewed as a chaotic, self-sustaining oscillation balancing the need for food at depth with the need for oxygen at the surface, the researchers used a dynamic systems chaos approach to uncover patterns in the seemingly chaotic collective behavior.

Their analysis revealed a 24-hour dive cycle during the spring, with whales swimming deepest during the day to follow their prey’s daily movements to the surface, a phenomenon known as vertical migration.

“We found that forager whales dive deeper during the day in spring and that this diving behavior is clearly synchronized with their vertically migrating prey,” Heide-Jørgensen said. “It has not yet been demonstrated for spring and remains controversial for autumn.”

The surprising plans of synchronized diving

The team also made the surprising discovery of two bowhead whales performing synchronized dives for a week, despite being separated by about a hundred kilometers. The pair, a female and an unknown sex, were sometimes five kilometers apart, sometimes hundreds of kilometers apart, but dived to different depths for up to a week. Synchronization was observed when they were within acoustic range of each other, which could exceed 100 kilometers, but the researchers did not record the whales’ vocalizations to determine whether they were interacting, as this remains a technically challenging task.

“Without direct observations, such as recordings of two whales, it is impossible to determine whether individuals are talking to each other,” Teilmann said, but “the observed subsurface behavior may be the first evidence supporting the acoustic swarm theory of long-term existence – the range of signals in whales, proposed by Payne and Webb in 1971.”

“The possibility of acoustically linked whales appearing to dive alone but actually being together is intriguing. Our study lays the groundwork for studying the sociality and behavior of such wildly mobile, unrestrained marine animals, and we encourage the research community to collect more concurrent tag data to confirm whether our interpretation is valid,” Podolsky concluded.