A new understanding of how the narwhal behaves came from a study of an adult male whose movements were recorded for 83 days by a satellite time and depth recorder attached to the animal's back.
"Despite the fact that ocean sensors on animals continue to improve and collect more data, there is a lack of adequate methods to analyse records of irregular behaviour," says Evgeny A. Podolsky, a geologist from Hokkaido University in Japan and the first author of the study.
In the hope of rectifying this, Podolsky merged with Mads Peter Hyde-Jorgensen, a marine biologist from the Greenland Natural Resources Institute, to develop a new way to detect patterns in seemingly random narwhal habits.
By combining their skills in signal processing and biology, Podolsky and Hyde-Jorgensen developed a method that uses mathematical techniques drawn from the theory of chaos to understand chaotic behaviour in dynamic conditions.
The theory of chaos is a study of activities that seem unpredictable, but are governed by a strict set of laws.
Researchers explain that these techniques can detect hidden conditions, known as "actors", to which chaotic systems tend to develop, and they can help scientists find undetectable patterns in some complex processes, including mysterious narwhal behavior.
The tools of chaos theory have helped unlock the hidden mode of the day, including new details on how these habits can be influenced by variables such as seasonal changes.
This is what they found: the narco tended to rest closer to the surface around noon, but when he did dive at that time, he dived in particularly deep.
Researchers report that dives at night and at night took place in shallower waters, but they were also more intense, perhaps because they hunted squids.
The study found that the narwhal had also adapted its behaviour in response to the prevalence of sea ice; it had not only reduced its activity on the surface during periods when the sea ice was more abundant, but had also shown more intense diving behaviour.
Narvals are not listed as endangered species by the International Union for Conservation of Nature, but are still considered vulnerable to human activity, from shipping and water pollution to climate change, and some populations may be threatened with extinction.
The life of the Narvals is closely linked to sea ice, which is rapidly declining as a result of global climate change, and information about their behaviour may be useful for their protection.
Researchers also write in their work that the theory of chaos can be useful for a broader analysis of animal behaviour, which will help to understand the problems faced by wild Arctic animals, for example because of the rise in temperature, although this approach is still in its infancy.
Further research will be needed, as the new study is based only on the behaviour of one individual.
However, they cover an "unusually long period" of almost three months, adding researchers, noting that comparable records often cover only a few days.
"Our approach is relatively easy to implement," explained the authors, "and can display and label long-term data, identifying differences between individual animals and different species, as well as the disturbances in behaviour caused by changing influences."