The narwhal (Monodon monoceros) is a type of porpoise related to bottlenose dolphins, belugas, harbor porpoises, and orcas, that lives in arctic coastal waters and rivers. Narwhals are 4 to 6 meters in length (13 to 20 feet) and weigh around 1000 kg. Narwhals are known as the unicorn of the sea due to their ivory tusk tooth that grows through the narwhal’s upper lip. In males, this tooth or spiral tusk grows up to 3 meters (10 feet) in length. Female narwhals sometimes grow a small tusk. The purpose of the tusk is thought to be for mating rituals or for battling rival suitors.
Narwhals are considered to be medium-sized toothed whales (odontocetes) and are similar in size to the beluga. Narwhals lack a dorsal fin but possess a dorsal ridge of about 5 cm, which researchers use to distinguish narwhals from each other. Unlike other whales (cetaceans), narwhals have convex tail fins. On their back, narwhals are mottled black and white, grey, or brownish. The rest of their body and underside is white. Newborn narwhal calves are pale grey to light brown. The coloring becomes darker as Narwhals age but then becomes progressively pale in later years. The coloring of narwhals can provide information about approximate age. Narwhals are thought to live to about sixty years but may live up to one hundred years.A hybrid whale called a narluga was discovered and shown by tooth DNA analysis to have been born from a beluga father and a narwhal mother, but it is not known how often this occurs.
The narwhal rarely travels south of the 60th parallel, remaining in Arctic waters year-round. In addition to the most common location in the Canadian Arctic and Greenland, narwhals have been observed off the coasts of Labrador, Iceland, Norway, the North Sea near the British Isles, Netherlands, Germany, Russia, and northern Alaska. Narwhals migrate about 1000 km or more to different areas in winter and summer. During migration, hundreds or thousands of narwhals may be seen traveling together. Outside of migration, narwhals remain in smaller groups of about three to eight individuals.
Narwhals spend winter, from November to April, in deep, ice-covered waters where upwelling currents bring extra nutrients to the ecosystem. The compact mobile ice on the surface provides protection from harsh seas and predators and access to air for breathing. In spring, narwhals are found at the floe edge (Sinaaq in Inuktitut), where open water meets the ice attached to the shoreline. In July and August, narwhals are dispersed over regions of the Canadian High Arctic archipelago. The bays, island passages, and fjords provide access to deep, open waters as well as shelter from the winds and predators. In the summer, narwhals take shorter, shallower dives.
Orca are the major predator of the narwhal, but Greenland sharks, polar bears, and walruses have also been reported to prey on narwhals.
Cod and squid are common food items in summer. During the winter, narwhals also eat halibut and turbot, a deep water fish. Shrimp are also part of the narwhal diet. In deep water, the narwhal uses echolocation to find food.
The narwhal’s tusk is one of two upper incisor teeth. While one tooth grows out from the upper jaw, the second smaller incisor tooth often remains embedded in the skull. In 1.5 percent of narwhals, the second incisor tooth develops into a second tusk. The tusk may serve a secondary sexual character similar to deer antlers. While most male narwhals have a tusk, only 15 percent of females have one. The tusk has been proposed to serve as a sensory organ detecting temperature, salinity, or pressure changes with the high quantity of tubules and nerve endings in the dental pulp. Although is it popularly believed that Narwhals use their tusks to break through sea ice, this has not been observed.
The myth of the unicorn is thought to have originated from the Indian rhinoceros, described by the Greek physician Ctesias in the fourth century BCE, which came to be known as monoceros by the Greeks and later unicornus by the Romans. As narwhal tusks were introduced into the European market, distributed by Viking sailors, these elegant and strikingly beautiful artifacts were thought to be unicorn horns and are thought to have changed the concept of the unicorn. Coinciding with the distribution of narwhal tusks, artwork featuring the unicorn changed from beast-like creatures that were vaguely equine in nature, to more graceful beings.