Narwhals are toothed, Arctic cetaceans, best known for the prominent tusk of the adult male. The latter is actually an outward eruption of the upper, left incisor, which develops into an elongated, twisted tusk; up to 10 feet long, it is used for mating jousts but may also serve other purposes (chemical sensing, communication etc.). A small minority of males have a pair of these structures and some females grow a short, narrow tusk.
Their name (Norse for "corpse whale") reflects their blotchy skin pattern, tubular shape and habit of lounging "belly up" on the surface of the ocean. After mating in spring, these highly vocal whales congregate in shallow, coastal bays for the summer months; there, females give birth to calves conceived the previous spring (gestation averages 15 months). The calf nurses for 4-5 months and will stay with its mother for almost two years.
As summer gives way to autumn, the narwhals break into small pods, spending the colder months among the ice flows of the Arctic Sea. Protected by a thick layer of blubber, they will feed on cod, halibut, shrimp, squid and young seals; adult males grow to a length of 16 feet and weigh up to 1.8 tons (females are about 2/3 their size). Narwhal predators include polar bears, killer whales and some Native American tribes; despite a lifespan of 50 years, this species may be among the early victims of global warming.
