NARWHAL

also spelled Narwal, or Narwhale (species Monodon monoceros), small whale belonging to the family Monodontidae, found along coasts and, sometimes, in rivers throughout the Arctic. Mottled gray in colour, the narwhal is usually about 3.5 to 5 m (11.5 to 16 feet) long. It lacks a dorsal fin and has only two teeth, both at the tip of the upper jaw. The left tooth develops in the male into a straight tusk protruding forward from the upper lip. This tusk, prized in medieval times as the fabled horn of the unicorn, grows up to 2.7 m (8.9 feet) in length and is grooved on the surface in a left-handed spiral. Rare males may develop two tusks; females usually develop none. The tusk has no known function; it is believed to have developed as a result of sexual selection. The narwhal is a gregarious whale usually found in groups of 15 to 20. It feeds on fish, cephalopods, and crustaceans and is hunted by the Eskimos.