Narwhals are sometimes called sea unicorns because of the enormous tusk that grows from the upper jaw in males. Some scientists have speculated that narwhal tusks, which can grow almost as long as three meters (about 10 feet), might be enormous sensory organs that can detect subtle changes in temperature and pressure.
A Magical Cup?
In the Middle Ages, narwhal tusks were widely thought to be unicorn horns with magical, curative properties. Indeed, cups made from narwhal tusks (above) were thought to neutralize poisons and were highly valued. Elizabeth I, Queen of England in the 1500s, is said to have owned a tusk worth 10,000 pounds, the price of a castle.