Noise Pollution Is Coming for the Narwhals

The Arctic is changing, and this could have a major impact on one of the region’s most iconic species. 

A new study published in Biology Letters last month provides evidence that narwhals are sensitive to noises from shipping and oil exploration. This is something that could pose a problem for the animals as climate change enables more human activity in the region, and also help guide conservation best practices as the region transforms. 

“We think that it would be very important to think of sound when you are managing the Arctic,” study co-author Outi Tervo of the Greenland Institute of Natural Resources tells Treehugger in an email. 

Narwhals and Noise 

Narwhals, sometimes called the unicorns of the deep because of their long tusks, are “one of three true Arctic species” of whales that live in the far north year-round, Tervo says.

Because of their remote location, the animals are very difficult to study, according to a University of Copenhagen press release. However, scientists do know that sound is very important for the species. Their Arctic home is dark for half the year, and they hunt at depths of up to approximately 5,906 feet (1,800 meters). Therefore, narwhals find their way and their food through echolocation, the same strategy used by bats.

To find out how sounds from shipping or oil and gas extraction might interrupt this process, the research team worked with local hunters to net and tag six narwhals in a remote fjord in East Greenland. Tervo says the whales were difficult to approach at first but grew calm after their capture. 

“They are very interesting, very impressive animals to work with,” she says. 

The researchers parked a ship in the fjord and exposed the narwhals to two kinds of noise: the ship’s engine and an airgun typically used in oil and gas exploration. The results showed that the narwhals “are very sensitive to sound,” Tervo says. 

They determined this by listening for the animals’ buzzing rate. 

“Buzzes are some acoustic signals that all toothed whales and echolocating bats produce when they are feeding,” Tervo explains, which means that the researchers could use the buzzing rate to determine if the animals were foraging. What they found was that the buzzing rate declined by half when the ship was approximately 7.5 miles (12 kilometers) away and foraging stopped entirely when the ship was approximately 4.3 to 5 miles (7 to 8 kilometers) away. However, the whales still showed effects from the noise when the ship was within approximately 25 miles (40 kilometers). 

That the whales were impacted by a sound so far away means they can detect ship noises that read as part of the background noise of the ocean to human equipment. While researchers suspected this would be the case for narwhals, “this is the first time that we can actually show it,” Tervo says. 

A Changing Arctic 

Narwhals aren’t the only marine mammals impacted by an Arctic that is being transformed by the climate crisis. The region is warming more than two times faster than the rest of the world, according to NOAA’s 2021 Arctic Report Card. One consequence of this warming detailed in the yearly report is that the soundscape of the Arctic is changing. The melting of sea ice and more frequent storms means the ocean itself is louder.  Marine mammals that have changed their migration patterns are heard from longer and farther north, and arctic shipping between the Pacific and Atlantic is increasing, which brings with it a new set of noises. 

“Because extensive commercial shipping in the Arctic is a relatively new phenomenon, Arctic species may have a lower tolerance of, and react more strongly to, such noise,” K. M. Stafford of the University of Washington’s Applied Physics Laboratory wrote in the report. 

Tervo hopes her research can help policymakers determine how best to protect narwhals in particular from these new noises. For one thing, the research suggests that new shipping routes or oil and gas exploration in narwhal foraging areas could have a negative impact on the whales. For another thing, the study indicates that narwhals may be sensitive to human-made noises coming from farther away than previously thought. 

“Maybe we need to be more conservative when thinking of safety zones and impacted areas,” Tervo says. 

This study is only a part of Tervo and her team’s attempts to understand how the Arctic’s transformation may impact narwhals. The species is currently considered a species of “Least Concern” by the IUCN Red List. However, their East Greenland population is in “sharp decline,” according to the University of Copenhagen. Tervo predicts they will be “very sensitive towards climate change.”

That’s because, unlike bowhead or beluga whales—the other two Arctic species— narwhals are less flexible in their migration patterns, returning to the same winter and summer foraging grounds. An earlier study by Tervo and her team found that narwhals are dependent on cold water, which could be a problem as water temperatures warm. 

Understanding how narwhals respond to noise is part of this project. Tervo and her team have already published another study in June finding that narwhals move to avoid noisy vessels. Next, they want to examine the narwhals' physiological or locomotion responses to noise. If the whales both stop foraging and move more in response to noise, this could cause them to burn too much energy without being able to replenish it. 

Finally, they want to know how easily the narwhals might recover from noise exposure. 

“We would want to also see if our data can say something about if the animals can get used to the noise, if they have some ways of coping with it,” Tervo says.

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