Using chaos theory to analyze the behavior of famous Arctic whales has revealed a daily diving pattern and long-distance synchronization (approximately 100 km).
Bowhead whales are among the largest and longest-living creatures on the planet. They are essential to the health of the Arctic Ocean’s marine ecosystems, yet our understanding of their hunting and diving practices remains limited. In a new study set to be published in the journal Physical Review Research, a group of researchers from Japan, Greenland, and Denmark have found behavior patterns in these whales that may shed light on their foraging and social interactions.
Researchers Associate Professor Evgeny A. Podolskiy from the Arctic Research Center at Hokkaido University, Professor Jonas Teilmann from the Department of Ecoscience at Aarhus University, and Professor Mads Peter Heide-Jørgensen from the Department of Birds and Mammals at the Greenland Institute of Natural Resources examined 144 days of diving data from 12 bowhead whales that were tagged in Disko Bay, West Greenland. They approached the whales’ diving habits as a chaotic, self-regulating cycle that balances the need to hunt for food at deeper levels with the need for oxygen at the surface; this led them to apply a dynamical systems chaos method to find order within the seemingly random behavior.
Their research indicated a 24-hour diving cycle during the spring, revealing that the whales dive to greater depths in the afternoon to follow their prey—an occurrence known as diel vertical migration—as these creatures rise towards the surface throughout the day.
“Our findings show that foraging whales dive deeper during the spring daytime, coordinating their diving behavior with the vertical movements of their prey,” Heide-Jørgensen explained. “Previously, this pattern had not been documented in the spring season and had shown conflicting evidence in the autumn.”
The team also made an unexpected observation of two bowhead whales diving in sync for up to a week, even though they were as far as 100 kilometers apart. One was a female, while the sex of the other is unknown. They varied in proximity, being as close as five kilometers or as distant as several hundred kilometers, yet they would time their diving sequences closely for durations of up to a week, although at different depths. This synchronization was noted when they were within each other’s acoustic range, which can extend beyond 100 kilometers, though the researchers did not capture any sound recordings to explore possible interactions due to the technical challenges involved.
“Without direct evidence, such as recordings of the two whales, we cannot confirm that they were communicating,” Teilmann acknowledged, but went on to say, “this underwater behavior may represent the first evidence for the acoustic herd theory of long-distance signaling in baleen whales that was proposed by Payne and Webb in 1971.”
“The concept of whales that seem to be diving independently yet are acoustically connected is astounding. Our research establishes a framework for investigating the social behaviors and movement patterns of these unpredictable, free-ranging marine animals, and we encourage other researchers to gather more simultaneous tagging data to validate our interpretations,” Podolskiy concluded.
