Researchers find that narwhals' unusual response to stress may be leading them to eventual death. The so-called "unicorns of the sea" are evidently vulnerable to human interference and disturbance.
Human Disturbance
For many years, narwhals lived in isolation from humans in various locations in Greenland, Russia, and Canada. Although the Inuit people hunt them, polar bears and killer whales were the biggest threats to the species for a very long time. However, with the recent decline in Arctic ice, there has been an increase in human imposition on their habitats in the form of oil exploration, commercial fishing, and shipping traffic.
Researchers of a new study published in the journal Science explored the possible effects of human interaction on the previously isolated narwhals and found that the creatures' unfamiliarity with the fairly new dangers triggers stress reactions that could lead to their death.
Fight, Freeze, Or Flee
There are often three common responses to threats: fight, freeze, or flee. Among narwhals, when they are faced with threats such as polar bears or killer whales, they dive into deeper waters slowly. This way, it does not put too much stress on the heart.
To see just how narwhals react to the dangers they are not yet very familiar with, researchers attached temporary heart rate recorders to five narwhals in Greenland after being released from nets or rescued from stranding as a result of the hunt.
'Freeze-Flee'
Typically, a "freeze" response results in slower heart rates, whereas a "flee" response results in faster heart rates. Compared to the narwhals' natural response to their known predators, data showed that their reactions to the new threats resulted in a "freeze-flee" response wherein they made rapid dives after being freed, with their heart rates dropping as low as three to four beats per minute.
Researchers found that the confused response of the narwhals is problematic because instead of conserving oxygen, the "freeze-flee" response results in using up 97 percent of its oxygen reserves compared to just using 52 percent in later dives wherein they were not just rescued from nets or stranding.
"The impact of humans is a relatively novel danger for narwhals," said Terrie Williams of the University of California, Santa Cruz, one of the researchers of the study. As a result, narwhals tend to immediately want to get away from the area as fast as they can. As of now, researchers are still trying to figure out the impacts of the "freeze-flee" response on narwhals' health, especially with current data supporting the potentially lethal implications of such a response.
Unicorn Of The Sea
Narwhals are often dubbed as the "unicorn of the sea" because of the long tusks protruding from their heads. Narwhal tusks can grow to up to 10 feet. They live in Arctic waters and feed on halibut, cod, shrimp, and squid. They are marine mammals that can dive a mile and a half deep underwater.
As mentioned, natural threats to narwhals are polar bears and killer whales, but recent developments in the Arctic has increased the chances of collisions with shipping vessels and underwater noise pollution, which interferes with communication among narwhals and other whales.
