Excerpt adapted from The Unicorn of the Sea by the National Oceanic and Atmospheric Administration

The narwhal is a toothed whale, but it is different from all other toothed whales in that it has no teeth in its mouth. Instead, male narwhals have a single, long, straight tooth (or tusk) that protrudes two to three meters out of the upper left jaw. Females almost never have a tusk. The tooth grows in a counterclockwise spiral.
It is this tusk for which narwhals are best known. There are many legends about the tusk of the narwhal. It is essentially the origin of the myth of the unicorn—European whalers that were in the Arctic would catch narwhals and bring tusks back to Europe with great stories about what kind of animals the tusks were attached to. But in terms of the biology of the animal, the tusk is actually used for social structure, to establish hierarchies of dominance for the males within narwhal pods. Narwhals have a black-and-white mottled skin pattern an