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Narwhals: the Aquatic Unicorns of the Arctic

by Robert C. Brears Blog

The narwhal is an Arctic-based whale that spends most of its life in the waters off Greenland, Svalbard, Russia, and Canada. Some estimates put 90 percent of its total global population in Baffin Bay, between Western Greenland and Canada. Narwhals are in fact only one of three whale species that spend their entire lives in the Arctic, the others being bowhead and beluga whales.
Antarctic Peninsula

Regions: Arctic

Destinations: Greenland, Svalbard

Highlights: Narwhal

The meaning of the narwhal name

In Inuit, the narwhal is called qilalugaq qernertag, meaning “one that is good at curving itself toward the sky.” This name is a reflection of its behaviour, which involves curving its back when diving downward and curving its head upwards when lying on its back, with its tusk pointing straight to the sky. Observing this aquatic narwhal dance first-hand is one of the rare pleasures possible on an Arctic cruise.

The biology of narwhals

Narwhals have small rounded heads and short flippers with upturned tips. Males are larger than females, with the largest of the species reaching around 5 meters (16 feet) long. Their skin colour changes with age. Newborn narwhals are a blotchy, slate colour or blue-grey. Juveniles become blue-black, adults become a mottled grey colour, and old narwhals are nearly all white. They can live between 30 – 40 years and have only one real predator that journeys up to the Arctic regions: the orca, or killer whale. When feeding, narwhals create a vacuum that sucks up their food, which includes Greenland halibut, shrimp, Arctic cod, rockfish, flounder, and crab. 

All about the narwhal tusk

The narwhal is famous among Greenland travellers as well as passengers on Svalbard voyages due to its long ivory tusk that spirals out counter clockwise. However, it is not a tusk like an elephant’s, but an upper-left canine tooth. Some male narwhal’s even have two of them, while only 15 percent of females have the tusk at all.

Understanding the tusk’s purpose

To understand more about the narwhal tusk, scientists have partnered with various Arctic communities. By combining scientific research with Inuit knowledge, researchers aim to understand more about why the species have tusks and how they use them day-to-day. With more than 60 scientists integrating their research with Inuit knowledge, researchers have undertaken laboratory and field studies to investigate the physical and dental properties of the tusks. As the studies have an interdisciplinary nature, scientists have also conducted field expeditions and collected over 50 interviews with Inuit community members. One mystery scientists seek to uncover is why narwhal tusks break. Some of the knowledge collected regarding tusks breaking include descriptions of threatened narwhals immediately diving in shallow waters, hitting the sea floor, and breaking their tusks.

The narwhal’s sonar

Recently scientists discovered that the tusk of the narwhal enables them to “see” like no other animal on Earth. They found the narwhal to have the most precise sonar ever recorded: Making clicking sounds up to 1,000 per second, narwhals use the echoes to reconstruct their surroundings in the dark water below. Earlier research found that the narwhal tooth adapted from a tooth with hard, external enamel to a tooth that is sensitive to even the slightest stimuli. Scientists speculate that the tooth enables a more precise echolocation by letting sea water in through pores in the tusk’s tip. Soundwaves then travel through the shaft and touch nerve endings at the base of the tooth, near the head. This produces signals to the brain, enabling the narwhal to determine its surroundings. 

At home in the pack ice

Narwhals are well adapted to living in pack ice, with usually only around five percent in open water over the period of 1 February – 15 April. This proportion can diminish to as little 0.5 percent, which means that narwhals only have 150 – 400 square kilometres (57 – 154 square feet) of open water available for breathing within an area of 25,000 square kilometres (9,650 square miles). The mystery that remains today is why narwhals keep returning to the same area year after year despite the dense ice. One theory is that living there provides predictable prey, as the whales feed on northbound spring migration species that ensure females are in good condition for calving and nursing in late spring/early summer. Therefore, it could be speculated that these areas are favoured due to their constant supply of Greenland halibut in Baffin Bay.

Narwhal diving depths

In summer, narwhals typically dive down to depths ranging between 30 and 300 metres (100 – 1,000 feet), but the majority of the time they are in water depths of between surface-level and 50 metres (165 feet). During autumn, narwhal dive depths and durations increase when they migrate towards their wintering grounds. At their wintering grounds, they stay in a limited area for 6 months and make small movements with the cracking of the pack ice. During the winter period, the number of shallow dives drops off drastically, with narwhals taking some of the deepest dives known for a marine mammal: Up to 800 metres (2,600 feet) is commonly reached, though narwhals can go as deep as 1,500 metres (4,900 feet). Over the winter period, narwhals dive down to these depths around 18 – 25 times per day every day for 6 months. The duration of these deep dives is around 25 minutes. At these depths, the conditions are life threatening, as pressure exceeds 2,200 PSI in the pitch-black water.

The northward narwhals

Scientists have found two winter home ranges for the Baffin Bay population of narwhals, with different diving depths for each group. The first is in northern Davis Strait and southern Baffin Bay, containing Canadian narwhal summering stock from Admiralty Inlet and Eclipse Sound. The second is further north, in Melville Bay narwhal stock. Using tracking data of narwhales tagged in Admiralty Inlet, researchers found that narwhals dived to depths of over 1,000 metres (3,280 feet) and fed mainly on Greenland halibut, while narwhals tagged in Greenlandic waters dived to shallower depths between 200 – 400 metres (650 – 1,300 feet) and ate a more varied diet that included squid and shrimp.

Adapting to life in the deep waters

Narwhals can survive at depths where there is intense pressure and no oxygen due to some key adaptations. First, they have a compressible rib cage that is flexible, enabling the body to be squeezed as the water depth increases. Second, narwhals have high concentrations of myoglobin in their muscles, having twice as much as some seal species and eight times as much as terrestrial mammals. In fact, the typical narwhal can carry 70 litres (18.5 gallons) of oxygen in its lungs, blood, and muscles. This is enough oxygen to sustain the narwhal underwater for 20 minutes at a swim speed of one metre (three feet) per second. Third, narwhals have muscles designed for endurance swimming. These muscles require less oxygen compared to other species, such as dolphins, which have fast-twitch muscle fibres for powerful, quick swimming speeds. Fourth, narwhals have streamlined bodies, enabling them to glide effortlessly through the water towards the bottom. This minimises the amount of oxygen required to work the muscles, saving a lot of energy. As with all whales and dolphins, narwhals exhale before a dive, further limiting the gas exchange to the blood during deep dives. This also limits the chance of decompression sickness, since the whales have expelled most of the air from their lungs. Once their rib cage compresses, the lungs “collapse” and the air inside them is channelled into the trachea system.

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