Increased human traffic is a threat to rare narwhals

Narwhals living in the Arctic have been relatively undisturbed by modernity, only visited by small numbers of indigenous peoples. Now with the expansion of mechanized tourism, a booming human population and melting sea ice, this is changing. 

A growing human population with more access than ever to the Arctic is coming more in contact with the fabled narwhal, an iconic tusked whale. Even relatively small noises have been shown to disturb and interrupt natural behaviors of narwhals and other marine animals. Noises caused by mine blasting, explosions from seismic surveys and cruise ships can trigger stress in these shy animals, even from miles away. 

New research from the University of Copenhagen and the Greenland Institute of Natural Resources (Pinngortitaleriffik) has investigated how narwhals are impacted by noise pollution. 

Narwhals are usually hard to study, living in relatively inaccessible habitats in the far north. The team however, was able to tag a group of the whales in the Scoresby Sound fjord system of East Greenland. The researchers bombarded the animals with noises to observe their reactions. In particular, they tested a ship’s engine and a seismic airgun used for oil exploration.

“The narwhals’ reactions indicate that they are frightened and stressed. They stop emitting the click sounds that they need to feed, they stop diving deep and they swim close to shore, a behaviour that they usually only display when feeling threatened by killer whales. This behavior means that they have no chance of finding food for as long as the noise persists,” said study co-author Outi Tervo.

Unfortunately, narwhals are especially sensitive to sounds. Because the Arctic is dark for approximately half of the year, the whales evolved to live in complete darkness for a significant portion of their lives. Even in the brighter parts of the year, narwhals spend time at depths in the ocean that are still dark. 

To compensate for lack of visibility, the whales use clicks as part of a type of echolocation, similar to that used by bats. Unusual noises can disrupt navigation and normal behaviors of the narwhals. 

“Our data shows that narwhals react to noise 20-30 kilometers away from a noise source by completely stopping their clicking sounds. And in one case, we could measure this from a source 40 kilometers away. It is quite surprising that we can measure how something so far away can influence whale behavior,” said Susanne Ditlevsen of Copenhagen’s Department of Mathematical Sciences, who was involved in analyzing data on the research.

“Even when a ship’s noise is lower than the background noise in the ocean and we can no longer hear it with our advanced equipment, the whales can hear and distinguish it from other sounds in their midst. And so, to a degree, their behavior is clearly affected. This demonstrates how incredibly sensitive narwhals are.”

The scientists hope that their research can prompt lawmakers to create new regulations to protect narwhals in this remote part of the world from human disturbances. 

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By Zach Fitzner, Earth.com Staff Writer