Narwhal — the sea unicorn

The whale with a 3-metre tooth

The narwhal is a whale that lives among the Arctic ice. A twisted 'horn' 3 metres long sticks out of its head — but it's actually a tooth! Long ago people thought it was a unicorn's horn and sold it for more than gold. Narwhals dive 1.5 km deep. They 'greet' each other with their tusks.

The narwhal (Monodon monoceros) is a toothed whale (5 m, 1,600 kg) of the Arctic waters of Canada, Greenland and Russia. The male's left upper tooth grows in a spiral up to 3 m — with 10 million nerve endings it senses water salinity, temperature and pressure; drone footage in 2017 showed narwhals stunning fish with the tusk. In the Middle Ages tusks were sold as 'unicorn horns' — Queen Elizabeth I paid the price of a castle for one. It dives to 1,500 m for 25 minutes — among the deepest of any mammal. It breathes through holes in the ice; if the ice closes, it dies. About 170,000 remain; threats are climate change and ship noise.

Fun facts

• A narwhal's 'horn' is a tooth growing outward, with 10 million nerves inside.
• Queen Elizabeth I paid the price of a castle for one narwhal tusk.
• A narwhal dives 1.5 km deep — a sixth of Everest's height.