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The Narwhal (Monodon monoceros) is an Arctic species of cetacean. It is a creature rarely found south of latitude 70°N. It is one of two species of white whale in the Monodontidae family (the other is the beluga whale). It is possibly also related to the Irrawaddy dolphin.
The most conspicuous characteristic of male narwhal is their single extraordinarily long tusk, an incisor that projects from the left side of the upper jaw and forms a left-handed helix. The tusk can be up to 3 metres (nearly 10 ft) long (compared with a body length of 7–8 m [23–26 ft]) and weigh up to 10 kilograms (22 lbs). About one in 500 males has two tusks, which occurs when the right tooth, normally small, also grows out. Although rare, a female narwhal may also produce a tusk. There is a single recorded case of a female with two tusks.
The purpose of the tusk has been the subject of much debate. Early scientific theories suggested that the tusk was used to pierce the ice covering the narwhal's Arctic Sea habitat. Others suggested the tusk was used in echolocation. More recently, scientists believed the tusk is primarily used for showmanship and for dominance: males with larger tusks are more likely to successfully attract a mate. This hypothesis was suggested by the activity of "tusking", in which two males rub their tusks together.
However, recent work by a research team led by Martin Nweeia suggests that the tusk may in fact be a sensory organ. Electron micrographs of tusks revealed millions of tiny, deep tubules extending from the tusk's surface, apparently connecting to the narwhal's nervous system. While such tubules are present in the teeth of many species, they do not typically extend to the surface of healthy teeth. The exact sensory purpose of the tusk remains unknown, but scientists now hypothesize that it may detect temperature, salinity, pressure, and/or particulate makeup of the water in which the narwhal swims. Unlike the tusks of elephants, narwhal tusks do not regrow if they break off. However if damaged the tusks can repair themselves to a certain extent.
Male narwhals weigh up to 1600 kg (3500 lb), the female around 1000 kg (2200 lb). Most of the body is pale with brown speckles in color, though the neck, head and edges of the flippers and fluke are nearly black. Older animals are usually more brightly colored than younger animals.
Behavior and diet
Narwhals are quick, active mammals which feed mainly on species of cod that reside under ice-enclosed seas.
In some areas their diet seems to have adapted to include squid, shrimp, and various fish, such as schooling pelagic fish, halibut, and redfish. Canadian Researcher William Sommers has found that when food is scarce, narwhals will even eat baby seals. Narwhals normally congregate in groups of about five to ten. Sometimes several of these groups might come together, particularly in summer when they congregate on the same coast.
At times, male narwhals rub their tusks together in an activity called "tusking". Recent findings of a marine mammal researcher at the Smithsonian Institution showed that the tusk also plays a role in the animal's sensory perception, with as many as 10 million tiny nerves present within the modified tooth. This suggests that the tusking may simply be a way of clearing encrustations from the sensory tubules, analogous to brushing teeth.
Narwhals are deep divers. During a typical deep dive the animal will descend at 2 m/s for eight to ten minutes, reaching a depth of at least 1,500 m (5,000 ft), spend perhaps a couple of minutes at depth before returning to the surface.
Population and distribution
The narwhal is found predominantly in the Atlantic and Russian areas of the Arctic. Individuals are commonly recorded in the northern part of Hudson Bay, Hudson Strait, Cottage Lake, Baffin Bay; off the east coast of Greenland; and in a strip running east from the northern end of Greenland round to eastern Russia (170°E). Land in this strip includes Svalbard, Franz Joseph Land, and Severnaya Zemlya. The northernmost sightings of narwhal have occurred north of Franz Joseph Land, at about 85°N.
The world population is currently estimated to be around 50,000 individuals. Most estimates of population have concentrated on the fjords and inlets of Northern Canada and western Greenland. Aerial surveys suggest a population of around 20,000 individuals. When submerged animals are also taken into account, the true figure may be in excess of 25,000.
Narwhals are a migratory species. In summer months they move closer to coasts. As the winter freeze begins, they move away from shore, and reside in densely-packed ice, surviving in leads and small holes in the ice. As spring comes these leads open up into channels and the narwhals return to the coastal bays.
Predation and conservation
The main predators of the narwhal are polar bears and orcas. Inuit people are allowed to hunt this whale species legally. The northern climate provides little nutrition in the form of vitamins which can only be obtained through the consumption of seal, whale, and walrus. The livers of these animals are often eaten immediately following the killing by the hunting party in an ancient ceremony of respect for the animal. In Greenland, traditional hunting methods in whaling are used (such as harpooning), but high-speed boats and hunting rifles are frequently used in Northern Canada. PETA and other animal rights groups have long protested the killing of narwhals.
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