The narwhal (Monodon monoceros), an iconic whale of remote Arctic waters, is widely known for its long, spiral tusk, which is really an elongated tooth. The tusk, which is predominantly found in males and can grow up to 10 feet long, is one of the most fascinating traits in nature and the inspiration for myths such as the unicorn. It is believed to play a role in competition for mates, including mating displays. The tusk may have other uses and its function is still debated, primarily because few people have observed how these elusive animals use their tusks in the wild.