Title: 
Headings: What Is a Narwhal?
Wonder of the Day #489
What Is a Narwhal?
Have You Ever Wondered...
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Content: In reality, though, a narwhal tusk is not a unicorn horn. In fact, it's not a horn at all. Would you believe it's a tooth? It's true! Male narwhals have a left incisor tooth that grows outward straight through the left side of the upper jaw. It can grow up to almost 10 feet in length with a distinctive spiral shape. Female narwhals also have a similar tusk that's much shorter and straighter. A narwhal's right incisor is normally small, but occasionally it also grows out. These “two-horned" narwhals are very rare. Scientists aren't completely sure what purpose narwhal tusks serve.