For most of human history, the narwhal existed only as a myth. European traders sold the tusk as “alicorn” — unicorn horn — at prices that exceeded gold, and the living animal behind it was so remote and so rarely seen that many educated people doubted it existed at all. The naturalist Ole Worm correctly identified the tusk as a whale tooth in 1638. It took another century before Europeans could confirm the animal with their own eyes. Today the narwhal is real, documented, and under pressure — the sea ice it depends on is disappearing at a rate that gives conservation scientists genuine cause for concern.

The narwhal tusk is not a horn. It is the upper left canine tooth — erupted through the lip and grown in a distinctive counterclockwise spiral throughout the male’s life.

Most males develop one tusk; roughly 15% grow two. Females almost never develop tusks. The tusk grows throughout life, reaching an average of 2 to 2.5 metres in adult males and up to 3 metres in the largest individuals. It accounts for roughly half the animal’s body length.

The tusk surface lacks enamel and is penetrated by up to 10 million microscopic nerve tubules that open directly to the ocean. This gives the narwhal the ability to detect minute changes in water temperature, salinity, and pressure through the tusk surface — a sensory capability unlike anything else in the cetacean world. Research published in 2014 confirmed these nerve tubules are functional, resolving a debate that had persisted for decades.

Beyond sensing, the tusk serves clear social functions. Males engage in “tusking” — crossing and rubbing tusks in ritualized contests that establish social dominance. Tusk length and condition signal genetic quality to females. And in 2017, drone footage captured a narwhal using its tusk to stun Arctic cod before eating them — the first direct evidence of the tusk as an active hunting tool.

Narwhals are among the most Arctic-adapted of all cetaceans — they live year-round in the high Arctic and do not migrate south in winter like most other whales.

Their range is centred on the waters of the Canadian Arctic Archipelago, Baffin Bay, Hudson Bay, and west and east Greenland. Smaller populations exist around Svalbard, Norway, and Franz Josef Land, Russia. The Pond Inlet area of Baffin Island is famous for summer aggregations of thousands of narwhals moving through the narrow straits.

In winter, narwhals move under heavy pack ice, maintaining breathing holes and navigating in near-total darkness to find prey on the seafloor. This behaviour — overwintering beneath pack ice rather than retreating to open water — is rare among whales and makes narwhals extraordinarily dependent on stable sea ice dynamics.

Narwhals are deep-diving predators that forage under sea ice at depths regularly exceeding 800 metres, targeting prey that most whales never reach.

Their diet shifts seasonally. In winter, Greenland halibut (turbot) is the dominant prey — flatfish that live on or near the seafloor at depth, hunted in complete darkness. In summer, Arctic cod becomes more important as fish shift shallower during the open-water season. Squid and shrimp supplement the diet year-round.

Narwhals lack functional teeth other than the tusk. They are suction feeders, drawing prey into the mouth by rapidly expanding the throat. The 2017 drone footage showing tusk use to stun cod before suction-feeding suggests the tusk plays a more active hunting role than the suction mechanism alone would suggest.

Yes — and the history of why this question needs asking says as much about European ignorance of the Arctic as it does about the narwhal itself.

For centuries, only the tusk reached European markets — brought south by Norse traders and later by Inuit traders who had always known the animal well. The tusk was sold as unicorn horn and priced higher than gold; Queen Elizabeth I reportedly paid the equivalent of a castle for one. The animal behind the tusk was too remote, too Arctic, and too unlike anything familiar to be easily believed. Ole Worm correctly identified the tusk as a whale tooth in 1638, but cultural belief in the unicorn was so entrenched that it took decades for the identification to be widely accepted.

The narwhal’s extraordinary specialisation for sea ice environments is precisely what makes it vulnerable — there is limited room to adapt when the habitat itself is disappearing.

• Sea ice loss — Arctic sea ice extent is declining. Narwhals overwintering under pack ice face changing prey distributions, altered acoustics, and increased risk of ice entrapment events
• Shipping traffic — opening Arctic sea routes increase ship noise, which disrupts narwhal echolocation and communication, and raises collision risk
• Oil and gas development — expanding exploration in Arctic narwhal habitat
• Hunting — regulated under Inuit traditional use provisions in Canada and Greenland; tusk trade continues under permit