Narwhal

 The narwhal is an Arctic toothed whale, closely related to the beluga whale and a cousin to the porpoise.  The adult male of the species is generally between 12 and 15 feet in length, weighing about 3,000 pounds.  The adult female is smaller: 10-12 feet long and weighing about 2,000 pounds.  Their skins are of a mottled black and white pattern.  What distinguishes the male narwhal from all other aquatic animals is its tusk.  The tusk is actually an enormously long tooth, a left incisor, that grows to a length of up to ten feet.  Rarely, male narwhals will exhibit two tusks, the second one being a right incisor.  Female narwhals have a very short tusk that barely extends outside the mouth.  The tusk is a secondary sexual characteristic, like the mane on a male lion.  There is little evidence to show that male narwhals engage in fighting or other aggressive behavior with other males.  Narwhals are primarily found in Arctic waters of eastern Canada and Greenland, but also live in waters around Iceland, Svalbard, Franz Joseph Land, and Severnaya Zemlya.  It is estimated that there are 75,000 narwhals, all living in Arctic waters.  This narrow biosphere makes them particularly susceptible to threats posed by climate change.  They feed mostly on halibut, cod, shrimp, and squid.  In the summer, narwhals congregate near shore.  In the winter, though, they move into deep, ice-infested waters.  There, narwhals perform dives almost unprecedented for marine mammals, sometimes reaching 5,000 feet and lasting 25 minutes.  The only natural predators of narwhals, and then mostly the young or infirm, are polar bears and killer whales.  Native Inuits have hunted narwhals for centuries, as they provide a valuable source of nutrition.  Vikings occasionally obtained narwhal tusks from the Inuit and then sold them as horns of the legendary unicorn, which were reputed to have magical powers.  Cups made from narwhal (unicorn) tusks were sold for fortunes.  Some whalers, knowing the truth, ventured north to hunt the narwhal.  It was only in the seventeenth century that Europeans became widely aware of the Arctic narwhal, causing the market for unicorn horns to collapse.