Narwhal

A tooth, not a horn

The narwhal’s famous “tusk” is actually an elongated upper-left canine tooth that erupts through the lip and grows in a left-handed spiral up to 3 meters long. About 15% of male narwhals develop two tusks; about 3% of females develop a tusk. The biology is unusual — most teeth grow downward; the narwhal tusk grows out of the lip and forward through the upper lip.

The function of the tusk was debated for centuries. Recent research suggests it serves multiple roles:

• Sensory organ — the tusk has 10 million nerve endings that detect changes in water salinity, temperature, and pressure.
• Hunting tool — narwhals have been filmed using their tusks to stun fish with a quick lateral strike.
• Social signaling — males rub tusks (“tusking”) in apparent communication.

Unicorn legend

For centuries in medieval Europe, narwhal tusks were sold as unicorn horns — supposed magical objects with healing properties. Vikings and other northern traders harvested narwhal tusks and shipped them south, where rulers paid extraordinary prices. Several European royal collections still hold “unicorn horns” that are actually narwhal tusks.

Deep divers

Narwhals are among the deepest-diving mammals — routinely diving 800–1,500 m, with recorded dives over 2,400 m. Each dive lasts up to 25 minutes. Their hemoglobin and myoglobin store unusually high oxygen reserves, and their flexible ribcage allows lung collapse without injury at extreme depth.

A polar specialist

Narwhals are among the few cetaceans that live their entire lives in the high Arctic, never migrating south. They thrive in dense pack ice, finding pockets of open water (polynyas) to surface and breathe. Climate change, which is destroying their pack-ice habitat, is the main long-term threat to the species.