Narwhals, also known as Monodon monoceros, are small whales that swim across the Arctic Ocean. They are known for their unique spiral tusks that protrude up to 10 feet from their faces. But another quirk of the species is that it dives in and out of the water for no apparent rhyme or reason.
New paper published in PLOS Computational Biology gives meaning to the narwhal’s seemingly random swimming. Using an area of mechanics and mathematics called “chaos theory,” this paper states that specific diurnal and seasonal patterns directly influence narwhal diving and surfacing behavior, despite appearances to the contrary.
A deep dive into narwhal behavior
Narwhals are some of the deepest diving whales in the world. They can descend to about 6,000 feet below the surface of the water. But while the diving abilities of narwhals are widely documented, whales apply these skills in ways that scientists cannot yet understand. In other words, experts simply cannot predict when these animals will dive, nor to what depth they will descend when they do.
“Adequate methods for analyzing records of irregular behavior are lacking,” study author Evgeny Podolski, a geophysicist at Hokkaido University, said, according to a press release.
That is, until now. Podolski and a colleague have devised a new way to study narwhal swimming that reveals previously unidentified diving and surfacing patterns when applied to individual narwhals in the wild.
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To identify the daily and seasonal swimming patterns of a wild narwhal, the team turned to “chaos theory,” a field of scientific research that inspects irregularities and identifies patterns in those irregularities that would otherwise be difficult to detect without sophisticated mathematics.
Applying the tools of this theory to swimming depth data from a single tagged narwhal over a period of about 80 days, the team identified new patterns of diurnal activity. Specifically, they found that the tagged individual tended to stay on the surface of the water around midday, but went down deep when it decided to dive. Alternatively, the animal tends to dive for extended periods at reduced depth at night, potentially due to increased predatory activities at that time.
In addition to these daily patterns, the analysis also revealed that narwhal diving and surfacing varied with the seasons. In fact, the narwhal avoids the increasingly frozen surface of the water as the weather cools, leading to more intensive diving during the ice season.
“Our approach is relatively easy to implement and can map and label long-term data, identifying differences between the behavior of individual animals and across species, as well as detecting disruptions in behavior caused by changing influences,” said the two study authors, according to a press release.
Ultimately, the researchers concluded that their method could contribute to the future conservation of the narwhal, as well as other Arctic animals struggling to adapt to changes in sea ice and other forms of climate change.