Narwhals live in Arctic waters and are known as unicorns of the sea. Their long tusk is in fact an outgrown tooth. It is almost like a piece of skin in the sense that it has all the sensory nerve endings that can sense the changes in the salinity of the water. Narwhals are shy and skittish; they do not have any tooth in the mouth, and eat relatively small prey.
獨角鯨分布在北極水域，有海洋獨角獸之稱。牠的長角其實是外長的牙齒，幾乎像皮膚一樣有各種感覺神經，可以探測海水的鹹度。牠生性害羞，嘴內無牙，並以小魚為食。