narwhal

 

(när'wəl) , a small arctic whale, Monodon monoceros. The males of this species, and an occasional female, bear a single, tightly spiraled tusk that measures up to 9 ft (2.7 m) in length. This tusk is an overgrown upper central incisor tooth, generally the one on the left. Very rarely do both incisors grow out in this manner; the animal is otherwise toothless. The tusk is nerve-rich and may be used as a sense organ and for other functions. The narwhal is short-headed and virtually snoutless. When mature, it is mottled gray in color. Like its close relative the beluga, it lacks a dorsal fin, but it does have a long, low dorsal hump. The narwhal may reach a length of 20 ft (6.1 m), excluding the tusk. It is found in the Arctic and N Atlantic oceans, occasionally as far south as Britain; narwhals usually travel in groups of 15 to 20 animals. The diet of narwhals consists chiefly of cuttlefish and cod. Mating occurs in the summer, and after a gestation of 14 months the female gives birth to a single blue-gray calf measuring up to 5 ft (1.5 m). The calves are weaned at six months. Formerly killed for its tusk, which was believed to have magical properties (and was sold for centuries as a unicorn horn), the narwhal is now hunted by native peoples for food and for the tusk. It is classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Cetacea, family Monodontidae.

Bibliography

See studies by F. Bruemmer (1993) and J. Rosing (1999).

Narwhal
Size comparison against an average human
Conservation status
Data deficient (IUCN)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Cetacea Family: Monodontidae Genus: Monodon Species: M. monoceros
Binomial name
Monodon monoceros Linnaeus, 1758
Narwhal range (in blue)

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.

Taxonomy

The Narwhal was one of the many species originally described by Linnaeus in his 18th century work, Systema Naturae.^[1] The English name narwhal is derived from the Dutch name narwal which in turn comes from the Danish narhval which is based on the Old Norse word nár, meaning "corpse." This is a reference to the animal's colour. The narwhal is also commonly known as the Moon Whale. In some parts of the world, the Narwhal is colloquially referred to as a "reamfish." In Inuit language the narwhal is named Tuugaalik.

Description

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.^[2]

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.^[3] 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.

Behaviour 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^[4]. 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.

Cultural References

In Inuit legend, the narwhal was created when a woman holding onto a harpoon had been pulled into the ocean and twisted around the harpoon. The submerged woman was wrapped around a beluga whale on the other end of the harpoon, and that is how the narwhal was created.

Some medieval Europeans believed narwhal tusks to be the horns from the legendary unicorn.^[5] As these tusks were considered to have magic powers, Vikings and other northern traders were able to sell them for many times their weight in gold. The horns were used to make cups that were thought to negate any poison that may have been slipped into the drink. During the 16th century, Queen Elizabeth received a carved and bejeweled narwhal tusk for £10,000 - the cost of a castle - which she used as a sceptre.^{[citation needed]} The tusks were staples of the cabinet of curiosities.

The truth of the tusk's origin developed gradually during the Age of Exploration, as explorers and naturalists began to visit Arctic regions themselves. In 1555, Olaus Magnus published a drawing of a fish-like creature with a horn on its forehead, while in 1577, Martin Frobisher depicted the horn going forward. The definitive end to the legend came in 1638, when Danish zoologist Ole Wurm gave a public lecture on the narwhal's tusks. In Jules Verne's novel Twenty Thousand Leagues Under the Sea, the submarine Nautilus is initially believed to be an unclassified subspecies of narwhal.

Gallery

Narwhal drawing

References

General references

• Cetacean Specialist Group (1996). Monodon monoceros. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes justification for why this species is listed as data deficient
• "Narwhal." M. P. Heide-Jorgensen (pp 783–787), in Encyclopedia of Marine Mammals, Perrin, Wursig and Thewissen eds. ISBN 0-12-551340-2
• "It's Sensitive. Really." William J. Broad, New York Times, 13 December 2005, http://nytimes.com/2005/12/13/science/13narw.html / NYT article RSS link
• Narwhal general information
• Narwhal Tooth Expedition and Research Investigation
• Narwhal info
• "Narwhal Found to Have a Trick Up Its Tusk", Scientific American News

External links

• Whale and Dolphin Conservation Society (WDCS)
• Narwhal Whales Information and images

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