Narwhals are so bizarre that scientists have used chaos theory to explain their behavior: ScienceAlert

Narwhals are enigmatic marine mammals that fascinate us with their unique appearance and secret way of life under the Arctic sea ice.

Yet while we still have a lot to learn about narwhals – including how to save some endangered populations from ourselves – scientists have also made some key discoveries in recent years.

Known for their remarkably deep dives nearly 2 kilometers (1.2 miles) below the surface and their reliance on sea ice for their life cycle, the narwhal’s movements across the oceans are a complicated affair to track.

Now, with a little help from chaos theory, researchers have managed to shed light on what appeared to be irregular daily behavior in the movements of narwhals off the coast of east Greenland.

Group of narwhals in northern Canada, August 2005. (Image courtesy of Kristin Laidre via NOAA)

“While animal-based ocean sensors continue to advance and collect more data, there is a lack of adequate methods to analyze records of irregular behavior,” said Evgeny A. Podolskiy, a geoscientist at Hokkaido University in Japan and first author of the new study.

Hoping to remedy this, Podolskiy teamed up with Mads Peter Heide-Jørgensen, a marine biologist at the Greenland Institute of Natural Resources, to develop a new way to find patterns in the seemingly random habits of narwhals.

chaos theory is the study of an activity that seems unpredictable, but is governed by strict sets of laws.

Like the proverbial butterfly that unleashes a hurricane with a flapping of its wings, it’s a case of reliable physics accumulating in a way that no system can keep up with.

Likewise, like many animals, the narwhal’s meanders don’t enlighten our human brains about their daily activities.

The new insight into narwhal behavior came from an adult male narwhal, whose movements were recorded over an 83-day period by a satellite-linked time-depth recorder strapped to the animal’s back.

Close up of a narwhal having a tracker strapped to its back
Attaching a satellite-linked transmitter to a narwhal captured alive in Scoresby Sound, East Greenland. (Greenland Institute of Natural Resources)

Combining their respective specialties in signal processing and biology, Podolskiy and Heide-Jørgensen have developed a method that uses mathematical tactics borrowed from chaos theory to make sense of chaotic behavior in dynamic contexts.

These techniques can reveal hidden states, called “attractors”, towards which chaotic systems tend to develop, explain the researchers.

They can help scientists find hard-to-detect patterns in certain complex processes, including the cryptic behavior of narwhals.

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Chaos theory tools have helped unveil a hidden daily pattern for this narwhal, including new details about how these habits may be influenced by variables such as seasonal changes.

Here’s what they found: The tagged narwhal tended to rest closer to the surface around noon, but when it dived at that time, it dived particularly deep.

Dusk and night dives occurred in shallower water but were also more intense, the researchers report, possibly because the narwhal hunted the squid.

The narwhal also adjusted its habits in response to the prevalence of sea ice, the study found.

Not only did it reduce its surface activity at times when sea ice was more plentiful, the researchers report, but it also exhibited more intense diving behavior.

Narwhals are not listed as an endangered species by the International Union for Conservation of Nature, but they are still considered vulnerable to human activities, from shipping and water pollution to climate change. Some populations are in danger of disappearing.

Narwhals’ lives are closely tied to sea ice, which is rapidly shrinking due to global climate change, and information about their behavior could be invaluable in protecting them.

Chaos theory could also be useful for analyzing animal behavior more broadly, the researchers write.

This could help us understand the challenges other Arctic wildlife face due to rising temperatures and melting sea ice, for example, although this approach is still in its infancy.

More research (and more narwhals) will be needed, since the new study is based solely on an individual’s behavior.

Nevertheless, it covers “an unusually long period” of almost three months, the researchers add, noting that comparable recordings often only cover a few days.

“Our approach is relatively simple to implement,” the authors explain“and can map and label long-term data, identify differences between the behavior of individual animals and different species, and also detect disturbances in behavior caused by changing influences.”

The study was published in Computational Biology PLOS.

Sharon D. Cole