The charismatic narwhal is the legendary 'unicorn of the sea'. It's also thought that narwhal horns used in trade or washed up on beaches gave credence to the myth of unicorns on land. The horn is more properly called a tusk. Narwhals only have two teeth and in the males, the left one grows out of the jaw into a long spiralled tusk that can reach 2.5m in length and is prone to breaking. Suggested uses for such an impressive appendage include to spear food, for defence and as a weapon for competing males. However, its most likely use is to impress females, as an indication of the fittest mate. Narwhals are inhabitants of Arctic waters and are found at all depths. They tend to stay close to loose pack ice, where breathing holes are maintained through the sheets of ice.

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