The narwhal is the unicorn of the sea, a pale-colored porpoise found in Arctic coastal waters and rivers. These legendary animals have two teeth. In males, the more prominent tooth grows into a sword like, spiral tusk up to 8.8 feet (2.7 meters) long. The ivory tusk tooth grows right through the narwhal's upper lip. Scientists are not certain of the tusk's purpose, but some believe it is prominent in mating rituals, perhaps used to impress females or to battle rival suitors. Females sometimes grow a small tusk of their own, but it does not become as prominent as the male's.
--- From National Geographic
To learn about the narwhal, check out the following website: http://animals.nationalgeographic.com/animals/mammals/narwhal/
Like all whales, narwhals need to surface for air. However, global warming has been causing more rainstorms in the Arctic, which can quickly turn open areas of water into impenetrable ice sheets, preventing the narwhal from surfacing for air. In fact, oceanographers have enlisted a group of narwhals to track the earth's changing climate by fitting them with sensors to record changes in ocean depth and temperature.
What is that in the Arctic sea?
That creature with a single horn?
Some sailors saw it long ago
And thought it was a unicorn.
From: Polar Bear, Arctic Hare
Poems of the Frozen North
by Eileen Spinelli