Noise Threatens Narwhals, New Study Finds

A 3D rendering of narwhals - called 'the unicorns of the sea' because of the male's long single tusk. Getty/dottedhippo

For millennia, vast expanses of the Arctic Ocean have been untouched by humans, ocean where narwhals and other marine mammals lived undisturbed. Now that climate change is causing sea ice to melt, there has been an uptick of human activity in the Arctic. This has resulted in significantly more noise from an array of human sources, including seismic surveys, mine blasts, port projects and cruise ships.

Although the noise is not violently loud when it comes from a fair distance, for narwhals, the noise is disturbing and triggers stress -- even many kilometers away. These are the results of unique experiments conducted with the iconic whale.

The study, published in the journal Biology Letters on December 18, was carried out by the University of Copenhagen in partnership with the Greenland Institute of Natural Resources.

Narwhals are notoriously difficult to study because they only live in the hard-to-reach High Arctic, which is often covered by ice. But the research team managed to tag a herd of narwhals in the Scoresby Sound fjord system of East Greenland using a variety of measurement equipment. They then positioned a ship in the fjord, which exposed the animals to noise -- both from the ship's engine and from 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 behavior 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," explains marine biologist Outi Tervo of the Greenland Institute of Natural Resources, who is one of the researchers behind the study.

Tervo noted that the whales make an uncommon number of strokes with their tails when fleeing from noise. This may pose a danger to them because it vastly depletes their energy reserves.

Constant energy conservation is important for narwhals as they need a great deal of oxygen to dive several hundred meters below the surface for food and return to the surface for air.