The narwhals are odontocetes, but differently from all other toothed whales, male narwhals have a single long, straight tooth (or tusk) reaching nearly 3 m in length out of the upper left jaw while females almost never have a tusk. The tooth grows in a counterclockwise spiral. There are many legends about 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.

In terms of the biology of the animal, the tusk is actually used for social structure, to establish dominance hierarchies and ranks of males within narwhal pods. Not much is known about narwhals: they spend most of their lives in inaccessible areas of the Arctic which makes their behaviours nearly impossible to study. What we do know is that narwhals have adapted to be one of the deepest diving marine mammals, capable diving more than 1,800 meters deep. Their primary preys include the Greenland halibut, polar and Arctic cods, shrimps and squids.