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Narwhals, Monodon monoceros

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Description & Behavior

Narwhals, Monodon monoceros (Linnaeus, 1758), are a gregarious species commonly found in groups or "pods" of sometimes up to 20 individuals, but most often in groups of 3-8, which are often segregated by sex. During the migratory season, smaller groups combine with other groups to form large herds. Narwhals measure 3.6-6.2 m in body length (average 4.7 m in males, 4 m in females) pectoral fins measure 30-40 cm tip to tip, and width of the tail flukes is 1-1.2 m. Average weight for male narwhals is 1,600 kg and 900 kg for females, about 1/3 of the weight consists of blubber. Compared to other cetaceans, narwhals have a small head, blunt snout, short rounded flippers, and convex rather than concave tail flukes. They have no dorsal fin, but they do have a ridge about 5 cm high that runs along the posterior end on the dorsal side that measures 60-90 cm long. Adult narwhals are pale gray or light brown on the dorsal side, white on the ventral side, some with spotted patterns.

Narwhals have 2 teeth located in the upper jaw; in males, the left tooth will grow to form a long straight tusk, hence the nickname "unicorn of the sea." The length of the tusk is between 1/3-1/2 as long as the length of the body. Tusks have measured up to 3 m and weighed 10 kg. In rare cases, the other tooth forms a tusk, both of which grow counterclockwise in a spiral. Also in rare cases, females have been seen with tusks. The bottom end of the tusk appears clean and polished, however the remaining tusk is often covered in algae. The tusks are made up of an outer layer of cement, an inner layer calcareous hard tooth material called dentine, and a pulp cavity rich in blood that holds the tusk in place. Narwhals often break tusks, however they are able to repair the damage with new dentine growth.

The exact function of the tusk was unknown, until recently, and was thought to be used for male to male competition or to spear food or stir up food from the ocean bottom. According to a Press Release from the Harvard Medical School dated December 13, 2005:

"Nweeia has discovered that the narwhal's tooth has hydrodynamic sensor capabilities. Ten million tiny nerve connections tunnel their way from the central nerve of the narwhal tusk to its outer surface. Though seemingly rigid and hard, the tusk is like a membrane with an extremely sensitive surface, capable of detecting changes in water temperature, pressure, and particle gradients. Because these whales can detect particle gradients in water, they are capable of discerning the salinity of the water, which could help them survive in their Arctic ice environment. It also allows the whales to detect water particles characteristic of the fish that constitute their diet. There is no comparison in nature and certainly none more unique in tooth form, expression, and functional adaptation."

M. monoceros live to over 50 years.

Narwhals harbor several species of commensal animals such as whale lice and certain nematodes.

World Range & Habitat

Narwhals, M. monoceros, are found in Arctic waters from eastern Canada to central Russia between 70°N-80°N. There are large concentrations in the Davis Strait, around Baffin Bay, and in the Greenland Sea. They are occasionally found in eastern Siberia, Alaska, and the western Canadian Arctic. They are an arctic species, however, some wandering individuals have been seen of the coast of Newfoundland, Europe, and the eastern Mediterranean. Narwhals are one of the northernmost cetacean species with a smaller range than other cetaceans. They tend to stay near the loose pack ice, where they maintain breathing holes, and prefer deep water, migrating with the seasonal advance and retreat of the ice. In the summer when ice cover is reduced in deeper water bodies, they migrate to smaller water bodies such as the heads of fjords.

Feeding Behavior (Ecology)

Narwhals, M. monoceros, feed on squid, fish, crustaceans, and mollusks. Because they have few functional teeth, they are thought to use suction and jets of water to uncover prey on the ocean bottom. They have flexible necks that allow them to scan broad areas for food.

Life History

The breeding habits of the narwhal, M. monoceros, are largely unknown. It is known that they breed seasonally between March-May and give birth about 15.3 months later usually in July-August. Females are thought to nurse for about 20 months. Narwhals mate in the water, belly to belly. Females give birth to a single calf most often, however in rare cases the birth of twins have been recorded. Calves are born tail first and measure 1.5-1.7 m long and weigh 80 kg. They are born with about a 25 mm thick layer of blubber.

Conservation Status & Comments

M. monoceros are often hunted for their "ivory" tusks, a practice that increased in the 1980's resulting in an effort to upgrade the CITES standings to Appendix I. Fortunately, tusk sales have since declined and the species remains Appendix II. Estimated Current Population: 25,000-45,000.

Narwhals are hunted in Canada and Greenland. The Inuit people hunt them for their skin (known as Muktaaq), which is traditionally eaten raw with a thin layer of fat. They also sell narwhal tusks to tourists and collectors.

Narwhals, Monodon monoceros, are classified as Near Threatened on the IUCN Red List of Threatened Species:

NEAR THREATENED (NT)

A taxon is Near Threatened when it has been evaluated against the criteria but does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for or is likely to qualify for a threatened category in the near future.

References & Further Research

Marine Biology Mystery Solved: Function of "Unicorn" Whale's 8-foot Tooth Discovered - Harvard School of Dental Medicine Researcher Announces Findings Today
Jefferson, T.A., S. Leatherwood, and M.A. Webber, FAO species identification guide, Marine mammals of the world, Rome, FAO. 1993. 320 p. 587 figs.
Whale and Dolphin Conservation Society (WDCS)
Klinowska, M. 1991. Dolphins, Porpoises and Whales. The IUCN Red Data Book. Gland, Switzerland: IUCN.
Minasian, S. 1986. The World's Whales. New York: Academic Press.
Reeves, R., S. Tracey. 1980. *Monodon monoceros*. Mammalian Species, 127: 1-7.

Research Monodon monoceros » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS

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