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Overview
Brief Summary
Description
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Mammal Species of the World
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- Original description: Linnaeus, C., 1758. Systema Naturae per regna tria naturae, secundum classis, ordines, genera, species cum characteribus, differentiis, synonymis, locis. Tenth Edition, Laurentii Salvii, Stockholm, 1:75, 824 pp.
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Biology
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Description
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Description
Narwhal (Monodon monoceros) is an arctic cetacean, famous for its tusk, belong to Monodontidae (one of two whale species in the family along with Delphinapterus luecas). They live in arctic coastal waters and rivers. They are known as seasonal migrants that travel between bays and fjords in the summer and deep offshore area heavily packed in ice in the winter. In summer months, they move closer to coast which is an ice-free waters (usually in shallow one) then move offshore in winter to a deeper waters with densely packed ice on top of it though sometime surfacing in small leads in the ice (Laidre et al, 2002). They prefer deep or offshore waters almost in all area of occurrence and rarely seen south of 65oN latitude (Hay and Manfield, 1989). Supported by their ability to do deep dives and blubber up to 35% of their body weight insulation, living in a deep freezing water by the winter is not a problem.
- Laidre, K.L., Heide-Jørgensen,M.P., & Dietz, R. 2002. Diving behaviour of narwhal (Monodon monoceros) at two coastal localities in the Canadian High Arctic. Canadian Journal of Zoology, 80, 624-635.
- Hay, K. A. and Mansfield, A. W. 1989. Narwhal Monodon monoceros Linneaus, 1758. In: S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, pp. 145-176. Academic Press, London, UK.
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Comprehensive Description
Biology
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Distribution
Range Description
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Geographic Range
Narwhals (Monodon monoceros) are regularly found eastwards from the Canadian Arctic to central Russia, but occur infrequently or rarely in eastern Siberia, Alaska, and the western Canadian Arctic. They mostly remain above the Arctic Circle year-round, but stragglers have been recorded around Newfoundland, Europe, and the eastern Mediterranean (Minasian, 1984).
Biogeographic Regions: arctic ocean (Native )
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UNESCO-IOC Register of Marine Organisms
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1318
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van der Land, J. (2001). Tetrapoda, in: Costello, M.J. et al. (Ed.) (2001). European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50: pp. 375-376
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1406
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MEDIN (2011). UK checklist of marine species derived from the applications Marine Recorder and UNICORN, version 1.0.
http://www.marinespecies.org/asteroidea/aphia.php?p=sourcedetails&id=149081
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National Distribution
Canada
Origin: Native
Regularity: Regularly occurring
Currently: Present
Confidence: Confident
Type of Residency: Year-round
United States
Origin: Native
Regularity: Regularly occurring
Currently: Present
Confidence: Confident
Type of Residency: Year-round
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Global Range: Locally abundant in the high Arctic. Local concentrations occur in Davis Strait, Baffin Bay and adjacent waters, and the Greenland Sea. Smaller numbers occur in Hudson Strait, northern Hudson Bay, Foxe Basin, and Barents Sea. Presence in the Beaufort, Bering, and eastern Chukchi seas is exceptional. Also occurs in "Soviet" Arctic (Leatherwood and Reeves 1983). Most common in the eastern Canadian arctic and west Greenland area (IUCN 1991, which see for further details on distribution).
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Range
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Physical Description
Morphology
Physical Description
Head and body length, exclusive of the tusk, is 360-620 cm, pectoral fin length is 30-40 cm, and expanse of the tail flukes is 100-120 cm. According to Reeves and Tracey (1980) average head and body length is about 470 cm in males and 400 cm in females and average weight is 1,600 kg in males and 900 kg in females. About one-third of the weight is blubber. Coloration becomes paler with age. Adults have brownish or dark grayish upper parts and whitish underparts, with a mottled pattern of spots throughout. The head is relatively small, the snout blunt, and the flipper is short and rounded. There is no dorsal fin, but there is an irregular ridge about 5 cm high and 60-90 cm long on the posterior half of the back. The posterior margins of the tail flukes are strongly convex, rather than concave or straight as in most cetaceans.
There are only two teeth, both in the upper jaw. In females the teeth usually are not functional and remain embedded in the bone. In males the right tooth remains embedded, but the left tooth erupts, protrudes through the upper lip, and grows forward in a counterclockwise spiral pattern to form a long, straight tusk. The tusk is about one-third to one-half as long as the head and body and sometimes reaches a length of 300 cm and a weight of 10 kg. In rare cases the right tooth also forms a tusk, but both tusks are always twisted in the same direction. Occasionally one or even two tusks develop in a female. The distal end of the tusk has a polished appearance, and the remainder is usually covered by a reddish or greenish growth of algae. There is an outer layer of cement, an inner layer of dentine, and a pulp cavity that is rich in blood. Broken tusks are common, but the damaged end is filled by new dentine growth (Reeves & Tracey, 1980).
Range mass: 900 to 1600 kg.
Range length: 400 to 470 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; ornamentation
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Size
Size in North America
Length:
Average: 4.7 m males; 4.1 m females
Weight:
Average: 1,580 kg males; 960 kg females
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Ecology
Habitat
Habitat and Ecology
Fish, squid, and shrimp make up the narwhal’s diet (Hay and Mansfield 1989; Heide-Jorgensen 2002), especially Arctic fish species, such as Greenland halibut, Arctic cod, and polar cod (the latter of which are often associated with undersides of ice) (Laidre and Heide-Jørgensen 2005a). Narwhals feed mostly in deep water and possibly at or near the bottom. Dives of up to nearly 1,500 m and 25 minutes are documented (Laidre et al. 2003), and there are some seasonal differences in the depth and intensity of diving (Laidre et al. 2002; Laidre et al. 2003). Predators include killer whales, polar bears, and possibly occasionally Greenland sharks and walruses (Hay and Mansfield 1989).
Systems
- Marine
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Monodon monoceros occupies one of the most northerly habitats of any cetacean species, between 70°N and 80°N, and seems to have more specific habitat requirements, and thus a more restricted range, than other cetaceans. Narwhals are rarely found far from loose pack ice and they prefer deep water. There are large concentrations in the Davis Strait, around Baffin Bay, and in the Greenland Sea. The advance and retreat of the ice initiates migration.
During summer, narwhals occupy deep bays and fjords; the best known and probably largest narwhal population in the world inhabits the deep inlets, sounds and channels of the eastern Canadian Arctic and north-west Greenland. When ice cover is low in larger, deeper water bodies, they move to smaller water bodies, which are steep-sided and deep. These traditional summering areas at the heads of fjords are probably important areas for calving. The narwhal’s preference for deep water in summer separates them from beluga whales which spend the summer mainly in shallow estuaries and bays (Klinowska, 1991).
Range depth: 400 to 800 m.
Habitat Regions: polar
Aquatic Biomes: pelagic ; coastal
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Habitat Type: Marine
Comments: Bays, fiords, and inlets in warmer months; moves south into deeper water when ice begins to form. Not often far from loose pack ice. Near northern Baffin Island in summer, made both shallow dives and deep (to 257 m) dives to bottom (Martin et al., 1994, Can. J. Zool. 72:118-125). Probably dive to depths of more than 1000 meters (Reeves, in Wilson and Ruff 1999).
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Migration
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Migrates between northerly summer range and winter range to south. Inshore movement in summer dramatic and predictable, coincides with breakup of ice cover. Annual migrations appear responsive to ice formation and drift. (Leatherwood and Reeves 1983).
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Trophic Strategy
Food Habits
Narwhals have a varied diet, feeding upon squid, fish and crustaceans. With few functional teeth this animal is thought to use suction and the emission of a jet of water to dislodge prey such as bottom-living fish and molluscs. Their highly flexible necks aid in scanning a broad area and the capture of more mobile prey.
Foods eaten include: Polar cod, Greenland halibut, flounder, salmon, herring, crustaceans and cephalopods (octopuses and squids).
Animal Foods: fish; mollusks; aquatic crustaceans
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )
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Comments: Known prey includes squid, polar cod, demersal fishes, and crustaceans (Leatherwood and Reeves 1983).
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Associations
Ecosystem Roles
Narwhals harbour several species of commensal animals such as whale lice and certain nematodes. They act to limit the populations of their prey species.
Commensal/Parasitic Species:
- Nematods
- Cestodes
- Trematodes
- Acanthocephalans
- Whale lice
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Predation
Some have suggested that the tusk is used for anti-predatory functions, this is unsupported by evidence. Nonetheless, the tusk, which can grow to 3 m, would be a formidable weapon.
Known Predators:
- killer whales (Orcinus orca)
- Greenland sharks (Somniosus pacificus)
- polar bears (Ursus maritimus)
- humans (Homo sapiens)
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Known predators
Orcinus
Somniosus microcephalus
Homo sapiens
Ursus maritimus
This list may not be complete but is based on published studies.
- Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org
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Known prey organisms
benthonic invertebrates
Boreogadus saida
non-insect arthropods
Actinopterygii
Mollusca
Crustacea
Based on studies in:
Arctic (Marine)
Canada, high Arctic (Ice cap)
This list may not be complete but is based on published studies.
- M. J. Dunbar, Arctic and subarctic marine ecology: immediate problems, Arctic 7:213-228, from p. 223 (1954).
- M. S. W. Bradstreet and W. E. Cross, Trophic relationships at High Arctic ice edges, Arctic 3(1)5:1-12, from p. 9 (1982).
- Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org
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Population Biology
Global Abundance
10,000 to >1,000,000 individuals
Comments: About 18,800 occur in Canadian waters in summer; no population trend is evident (Strong 1988). Total population in the 1980s probably was somewhere between 25,000 and 50,000 (Evans 1992; see also IUCN 1991). Further information on populations is needed (IUCN 1991).
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General Ecology
Large aggregations sometimes observed; these are subdivided into cohesive units of 20 or fewer individuals. Different sexes and ages may segregate or mix.
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Life History and Behavior
Life Cycle
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Life Expectancy
Lifespan/Longevity
Monodon monoceros may live up to 50+ years in the wild, yet attempts at captive breeding have been unsuccessful. Upon reaching the captive establishment, M. monoceros have only survived from 1 to 4 months. Considering the adult male can grow to 7m long, the species is usually too big to keep in captivity except at the largest of establishments (Klinowska, 1991).
Range lifespan
Status: wild: 30 to 55 years.
Range lifespan
Status: captivity: 1 to 4 months.
Average lifespan
Status: wild: 40.0 years.
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Lifespan, longevity, and ageing
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Reproduction
The mating system of narwhals is unknown.
Monodon monoceros is a seasonal breeder. The gestation period is about 15.3 months, with mating occurring in March-May and calving in July-August of the following year. Lactation duration is unknown, but thought to be comparable to the white whale (Delphinapterus leucas) of 20 months. The interval between successive conceptions is normally three years. Monodon monoceros copulate vertically in the water, belly to belly. Infant narwhals are usually implanted in the left uterine horn. A single calf is often the result of gestation, yet some twins have been recorded. Birth takes place tail first (Klinowska, 1991). The newborn is born with 25 mm of blubber. Calves usually measure between 1.5 and 1.7 m and weigh 80 kg. Physical maturity is attained at a length of 4 m and a weight of 900 kg in females and 4.7 m and 1600 kg in males. This usually corresponds to 4 to 7 years of age (Reeves & Tracey, 1980).
Breeding season: March to May
Range number of offspring: 1 to 2.
Range gestation period: 12 to 15.3 months.
Average gestation period: 13 months.
Range weaning age: 12 to 24 months.
Range age at sexual or reproductive maturity (female): 4 to 7 years.
Range age at sexual or reproductive maturity (male): 4 to 7 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
Average birth mass: 80000 g.
Average number of offspring: 1.
Young narwhals are capable of swimming soon after birth. They are nursed and protected by their mothers for extended periods after birth.
Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); extended period of juvenile learning
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Breeds in March-May. Single calf is born in summer after gestation of about 14-15 months. Lactation exceeds 1 year, may extend up to 2 years. Calving interval most often is 3 years. Males probably sexually mature in 8-9 years, females in about 4-7 years.
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Evolution and Systematics
Functional Adaptations
Functional adaptation
The tusks of male narwhals may detect chemicals related to ice formation, salinity, or prey using a vast network of fluid-filled tubules connected to the tusk's central nerve.
"It could be a jousting tool or an ice-breaker. It has even been attributed to the legendary unicorn. But the true purpose of the narwhal's spectacular spiral tusk has remained a mystery.
"Now Martin Nweeia at Harvard School of Dental Medicine and his colleagues have come up with another explanation. They believe the tusk, which can measure up to 2.75 metres, could act as a sensor, helping the narwhal to survive in its Arctic home by detecting chemicals associated with prey, ice formation and salt concentrations.
"Two tusks taken from recently caught narwhals were examined under an electron microscope. This revealed a vast network of around 10 million fluid-filled tubules connecting the tusk's central nerve to the surrounding water. Such tubules exist in human teeth, but are only exposed at areas of gum recession, where they cause extreme sensitivity. 'The last place you would expect to have something so sensitive is a cold Arctic environment,' says Nweeia. A further surprise came when a laser was used to map the chemical composition of the tusk, a technique called reflectance microspectroscopy. It revealed that the narwhal's tusk is 'inside out'. Most teeth are hard on the outside and soft inside, but the narwhal's tusk has a soft protein-rich exterior, while the inside is more mineralised. 'Everything about these findings is counter-intuitive,' says Nweeia." (Geddes 2005:6)
Learn more about this functional adaptation.
- Linda Geddes. 2005. What's the point of the narwhal's tusk?. New Scientist. 188(2531/2532):
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Molecular Biology and Genetics
Molecular Biology
Barcode data: Monodon monoceros
There are 11 barcode sequences available from BOLD and GenBank. Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
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Statistics of barcoding coverage: Monodon monoceros
Public Records: 2
Specimens with Barcodes: 15
Species With Barcodes: 1
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
Red List Criteria
Version
Year Assessed
Assessor/s
Reviewer/s
Justification
Across the global range of the species, subpopulations are subject to differing levels of threat and warrant individual assessment. Therefore, a caveat for the global listing as Near Threatened is that it assumes national and international management authorities will continue to monitor and manage harvest levels. Hunting with modern equipment in specific parts of Greenland and Canada represents the most long-standing and consistent threat to narwhals throughout their range. Several small and/or depleted subpopulations (e.g. West Greenland and Hudson Bay) warrant individual assessment as an immediate priority.
History
- 1996Data Deficient(Baillie and Groombridge 1996)
- 1994Insufficiently Known(Groombridge 1994)
- 1990Insufficiently Known(IUCN 1990)
- 1988Insufficiently Known(IUCN Conservation Monitoring Centre 1988)
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Monodon monoceros is listed as CITES Appendix II and IUCN Data Deficient. As in most ivory bearing mammals around the world, destruction of individuals for their ivory is a constant threat.
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: near threatened
- Klinowska, M. 1991. Dolphins, Porpoises and Whales. The IUCN Red Data Book. Gland, Switzerland: IUCN.
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National NatureServe Conservation Status
Canada
Rounded National Status Rank: N4 - Apparently Secure
United States
Rounded National Status Rank: NU - Unrankable
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NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
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Status
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Trends
Population
The estimated generation length for the narwhal according to Taylor et al. (2007) is 24 years, which means that the 3-generation window is 1936-2008.
Population Trend
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Threats
In West Greenland, catches have declined since 1993 with no significant sex bias. Heide-Jorgensen (2002) estimated the annual catch rate at 550 between 1993 and 1995. In 2004, the estimated catch in West Greenland was 294 (NAMMCO/JCNB 2005), including whales that were struck and lost. In contrast to West Greenland, there has been an 8% increase in catches in East Greenland since 1993 (NAMMCO/JCNB 2005).
The narwhal is actively hunted only in Canada and Greenland. In the eastern Canadian Arctic, the average reported landed catch per year from selected communities was 373 between 1996 and 2004 (NAMMCO/JCNB 2005). In Canada the majority of the communities take a greater proportion of males than females throughout the seasons. Annual catch statistics in Canada substantially underestimate the total numbers of narwhals killed due primarily to the incomplete reporting of whales that are struck and killed but lost (IWC 2000; NAMMCO/JCNB 2005; Nicklen 2007).
Narwhals supplied various staples in the traditional subsistence economy. Today the main products are mattak and ivory (Reeves 1993; Reeves and Heide-Jørgensen 1994; Heide-Jørgensen 1994; Nicklen 2007). Narwhal tusks from Canada and Greenland are sold in specialty souvenir markets domestically and also have been exported. However, in Greenland, the export of tusks is currently banned. In Canada, the quota system that had been in place since the 1970s was replaced by a community-based management system implemented in the late 1990s and early 2000s (COSEWIC 2004). The hunt is managed by local hunter and trapper organizations with harvest limits established in some communities. Compliance has been questionable (COSEWIC 2004). Under this system, removals from some summering aggregations are probably sustainable, however, there is concern that removals from other summering aggregations may not be (NAMMCO/JCNB 2005). In Greenland, a quota system was introduced in 2004 by the Greenland Ministry of Fisheries and Wildlife. The quota was set at 300 narwhals (of which 294 were taken), divided among municipalities of West Greenland. Compliance reportedly has been good (NAMMCO/JCNB 2005) although there is concern that catch limits may be set too high (IWC 2007, p. 52).
The effects of climate change on narwhals are uncertain. Narwhals are well adapted to a life in the pack ice as indicated by the fact that there is very little open water in their winter habitat (Laidre and Heide-Jørgensen 2005b). They spend much of their time in heavy ice and are vulnerable to ice entrapments where hundreds can become trapped in a small opening in the sea ice (savssat) and die. This occurs when sudden changes in weather conditions (such as shifts in wind or quick drops in temperature) freeze shut leads and cracks they were using. When entrapped whales are discovered by hunters, they normally are killed. A recent assessment of the sensitivity of all Arctic marine mammals to climate change ranked the narwhal as one of the three most sensitive species, primarily due to its narrow geographic distribution, specialized feeding and habitat choice, and high site fidelity (Laidre et al. in press).
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Comments: Subsistence hunting evidently does not pose a significant threat at current levels, but further data are needed; potentially threatened by pollution and activities associated with development of mineral and hydrocarbon resources (IUCN 1991).
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Management
Conservation Actions
The European Union (EU), with stronger CITES rules than other countries, has established an import ban on tusks (active since December 2004). Although Denmark belongs to the EU, it is unclear whether the ban on trade in narwhal ivory between Greenland and Denmark is being enforced.
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Needs: See IUCN (1991) for a discussion of conservation measures.
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Conservation
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Relevance to Humans and Ecosystems
Benefits
Economic Importance for Humans: Negative
There are no known adverse affects to humans.
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Economic Importance for Humans: Positive
Historically narwhals were a staple food source of many Arctic peoples. Arctic people used the narwhals body for a number of other uses. The blubber can be rendered for oil, the sinew used as thread, and the tusks traded and carved.
Positive Impacts: food ; ecotourism ; research and education
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Economic Uses
Comments: Long subjected to subsistence harvest for meat, blubber, skin, sinews, and tusk. Still hunted for subsistence (probably around 1000 killed annually in Canada and Greenland); no commercial harvest, though tusk enters international trade. See IUCN (1991) for a summary of historical exploitation.
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Risks
IUCN Red List Category
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IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia
Narwhal
The narwhal, or narwhale, (Monodon monoceros) is a medium-sized toothed whale that lives year-round in the Arctic. One of two living species of whale in the Monodontidae family, along with the beluga whale, narwhal males are distinguished by a long, straight, helical tusk, actually an elongated upper left canine. Found primarily in Canadian Arctic and Greenlandic waters, rarely south of 65°N latitude, the narwhal is a uniquely specialized Arctic predator. In the winter, it feeds on benthic prey, mostly flatfish, at depths of up to 1500 m under dense pack ice.[3] Narwhals have been harvested for over a thousand years by Inuit people in northern Canada and Greenland for meat and ivory, and a regulated subsistence hunt continues to this day. While populations appear stable, the narwhal is particularly vulnerable to climate change due to a narrow geographical range and specialized diet.[4]
Contents |
Taxonomy and etymology
The narwhal was one of the many species originally described by Linnaeus in his Systema Naturae.[5] Its name is derived from the Old Norse word nár, meaning "corpse", in reference to the animal's greyish, mottled pigmentation, like that of a drowned sailor.[6] The scientific name, Monodon monoceros, is derived from Greek: "one-tooth one-horn"[6] or "one-toothed unicorn".
The narwhal is most closely related to the beluga whale. Together, these two species comprise the only extant members of the Monodontidae family, sometimes referred to as the "white whales". The Monodontidae are distinguished by medium size (at around 4 m (13 ft) in length), forehead melons, short snouts, and the absence of a true dorsal fin.[7] The white whales, dolphins (Delphinidae) and porpoises (Phocoenidae) together comprise the Delphinoidea superfamily, which are of likely monophyletic origin. Genetic evidence suggests the porpoises are more closely related to the white whales, and that these two families constitute a separate clade which diverged from the Delphinoidea within the past 11 million years.[8]
Description
These are medium-sized whales, being around the same size as a beluga whale. Total length in both sexes, excluding the "tusk" of the male, can range from 3.95 to 5.5 m (13 to 18 ft).[9] Males, at an average length of 4.1 m (13 ft 5 in), are slightly larger than females, at an average of 3.5 m (11 ft 6 in). Typical adult body weight can range from 800 to 1,600 kg (1,800 to 3,500 lb).[9] Males attain sexual maturity at 11 to 13 years of age, when they are approximately 3.9 m (12 ft 10 in) long, and females attain maturity at 5 to 8 years old, when they are 3.4 m (11 ft 2 in) long.[9] The pigmentation of the narwhal is a mottled pattern, with blackish-brown markings over a white background. They are darkest when born and become whiter in color with age, with white patches developing on the navel and genital slit at sexual maturity. Old males may be almost pure white.[6][9][10]
The most conspicuous characteristic of the male narwhal is its single extremely long tusk, a canine tooth[11] that projects from the left side of the upper jaw and forms a left-handed helix. The tusk seems to grow slightly throughout life from 1.5 to 3.1 m (4 ft 11 in to 10 ft 2 in). Despite its formidable appearance, the tusk is hollow and weighs only around 10 kg (22 lb). About one in 500 males has two tusks, which occurs when the right canine, normally small and less straight, also grows out. A female narwhal has a shorter, and straighter tusk.[12] She may also produce a second tusk, but this occurs rarely, and there is a single recorded case of a female with dual tusks.[13]
The most broadly accepted theory for the role of the tusk is as a secondary sexual characteristic, similar to the mane of a lion or the tail feathers of a peacock.[6] This hypothesis was notably discussed and defended at length by Charles Darwin, in The Descent of Man, and Selection in Relation to Sex (1871). It may help determine social rank, maintain dominance hierarchies, or help young males develop skills necessary for performance in adult sexual roles. Narwhals have rarely been observed using their tusk for fighting,[14] other aggressive behavior or for breaking sea ice in their Arctic habitat.[6] Some narwhals have a second, small tooth in their mouths, but are essentially toothless.[9] The tusk may be a sensory organ.[15]
Distribution
The narwhal is found predominantly in the Atlantic and Russian areas of the Arctic Ocean. Individuals are commonly recorded in the northern part of Hudson Bay, Hudson Strait, 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° East). Land in this strip includes Svalbard, Franz Joseph Land, and Severnaya Zemlya.[6] The northernmost sightings of narwhal have occurred north of Franz Joseph Land, at about 85° North latitude.[6] Most of the world's narwhals are concentrated in the fjords and inlets of Northern Canada and western Greenland.
Behavior and diet
Narwhals have a relatively restricted and specialized diet. Their prey is predominantly composed of Greenland halibut, polar and Arctic cod, cuttlefish, shrimp and Gonatus squid. Additional items found in stomachs have included wolffish, capelin, skate eggs and sometimes rocks, accidentally ingested when whales feed near the bottom.[3][9][16][17] Due to the lack of well-developed dentition in the mouth, narwhals are believed to feed by swimming towards prey until it is within close range and then sucking it with considerable force into the mouth. It is thought that the beaked whales, who have similarly reduced dentition, also suck up their prey.[18]
Narwhals are a migratory species. As spring comes, these leads open up into channels and the narwhals return to the coastal bays.[4]
Narwhals exhibit seasonal migrations, with a high fidelity of return to preferred, ice-free summering grounds, usually in shallow waters. In summer months, they move closer to coasts, usually in pods of 10–100. In the winter, they move to offshore, deeper waters under thick pack ice, surfacing in narrow fissures in the sea ice, or leads.[17] Narwhals from Canada and West Greenland winter regularly in the pack ice of Davis Strait and Baffin Bay along the continental slope with less than 5% open water and high densities of Greenland halibut.[3] Feeding in the winter accounts for a much larger portion of narwhal energy intake than in the summer[3][17] and, as marine predators, they are unique in their successful exploitation of deep-water arctic ecosystems.
Most notable of their adaptations is the ability to perform deep dives. When on their wintering grounds, the narwhals make some of the deepest dives ever recorded for a marine mammal, diving to at least 800 meters (2,625 feet) over 15 times per day, with many dives reaching 1,500 meters (4,921 feet). Dives to these depths last around 25 minutes, including the time spent at the bottom and the transit down and back from the surface.[19] In the shallower summering grounds, narwhals dive to depths between 30 and 300 meters (90–900 feet).
Narwhals normally congregate in groups of about five to ten individuals, sometimes up to 20 outside the summer. Groups may be "nurseries" with only females and young or can contain only post-dispersal juveniles or adult males ("bulls"), though mixed groups can occur at any time of the year.[9] In the summer, several groups come together, forming larger aggregations. Such aggregations can contain from 500 to over 1000 individuals.[9] At times, bull narwhals rub their tusks together in an activity called "tusking".[16] This behavior is thought to maintain social dominance hierarchies.[16]
Mortality and conservation
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Normally, narwhals can live quite a long life, with lifespans of up to at least 50 years recorded. Mortality often occurs when the narwhals suffocate after they fail to leave before the surface of the Arctic waters freeze over in the late fall.[9] Starvation can also threaten their lives, especially in young whales. Although almost all modern predation of narwhals is by humans, a few natural predators also attack them on occasion. The primary natural predators are polar bears, who attempt to swipe narwhals at breathing holes and mainly target young whales, and killer whales (or orcas), pods of which can overwhelm a narwhal. Greenland sharks and walruses may take a few small young or weak and wounded adults, though this is likely quite rare.[9] Inuit people are allowed to hunt this whale species legally for subsistence. Narwhal has been extensively hunted the same way as other sea mammals, such as seals and whales, for its large quantities of fat which constituted one of the most important resources of the native people living in arctic regions. Almost all parts of the narwhal, meat, skin, blubber and organs are consumed. Mattak, the name for raw skin and blubber, is considered a delicacy, and the bones are used for tools and art.[6] The skin is an important source of vitamin C which is otherwise difficult to obtain. In some places in Greenland, such as Qaanaaq, traditional hunting methods are used, and whales are harpooned from handmade kayaks. In other parts of Greenland and Northern Canada, high-speed boats and hunting rifles are used.[6]
Narwhal have been found to be one of the most vulnerable arctic marine mammals to climate change. The study quantified the vulnerabilities of 11 year-round Arctic sea mammals.[4][20] Narwhals that have been brought into captivity tend to die of unnatural causes.[15] The world population is currently estimated to be around 75,000 individuals.[4] Approximately 25,000–50,000 breeding narwhal are believed to exist in the wild worldwide.[9]
Humans and narwhals
In Inuit legend, the narwhal's tusk was created when a woman with a harpoon rope tied around her waist was dragged into the ocean after the harpoon had struck a large narwhal. She was transformed into a narwhal herself, and her hair, which she was wearing in a twisted knot, became the characteristic spiral narwhal tusk.[21]
Some medieval Europeans believed narwhal tusks to be the horns from the legendary unicorn.[22] As these horns were considered to have magic powers, such as the ability to cure poison and melancholia, Vikings and other northern traders were able to sell them for many times their weight in gold. The tusks 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 (approximately £1.5–2.5 million in 2007, using the retail price index).[23] The tusks were staples of the cabinet of curiosities.[24] 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, correctly identifying it as a "Narwal".[24] The narwhal was one of two possible explanations of the giant sea phenomenon written by Jules Verne in his book Twenty Thousand Leagues Under the Sea. The other possible explanation was a man-made vessel, but that was not likely in the opinion of the narrator.
Herman Melville wrote a section on the narwhal in Moby Dick, in which he claims a narwhal tusk hung for "a long period" in Windsor Castle after Sir Martin Frobisher had given it to Queen Elizabeth.[25]
See also
References
- ^ Mead, J. G.; Brownell, R. L., Jr. (2005). "Order Cetacea". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 723–743. ISBN 978-0-8018-8221-0. OCLC 62265494.
- ^ Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Reeves, R.R., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K. (2008). Monodon monoceros. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 18 December 2008.
- ^ a b c d Laidre, K (2004). "Deep-ocean predation by a high Arctic cetacean". ICES Journal of Marine Science 61 (1): 430–440. doi:10.1016/j.icesjms.2004.02.002.
- ^ a b c d Laidre, K. L.; Stirling, I.; Lowry, L.; Wiig, Ø.; Heide-Jørgensen, M. P. and Ferguson, S. (2008). "Quantifying the sensitivity of arctic marine mammals to climate-induced habitat change". Ecological Applications 18 (2): S97–S125. doi:10.1890/06-0546.1. PMID 18494365.
- ^ (Latin) Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Holmiae. (Laurentii Salvii). p. 824.
- ^ a b c d e f g h i Heide-Jørgensen, M. P. and Laidre, K. L. (2006). Greenland’s Winter Whales: The beluga, the narwhal and the bowhead whale. Ilinniusiorfik Undervisningsmiddelforlag, Nuuk, Greenland. ISBN 978-87-7975-299-3.
- ^ Brodie, Paul (1984). In Macdonald, D. The Encyclopedia of Mammals. New York: Facts on File. pp. 200–203. ISBN 0-87196-871-1.
- ^ Waddell, V.G.; Milinkovitch, M.C.; Bérubé, M. and Stanhope, M.J. (2000). "Molecular Phylogenetic Examination of the Delphinoidea Trichotomy: Congruent Evidence from Three Nuclear Loci Indicates That Porpoises (Phocoenidae) Share a More Recent Common Ancestry with White Whales (Monodontidae) Than They Do with True Dolphins (Delphinidae)". Molecular Phylogenetics and Evolution 15 (2): 314–318. doi:10.1006/mpev.1999.0751. PMID 10837160.
- ^ a b c d e f g h i j k Macdonald, D.W.; Barrett , P. (1993). Mammals of Europe. New Jersey: Princeton University Press. ISBN 0-691-09160-9.
- ^ "Monodon monoceros". Fisheries andAquaculture Department: Species Fact Sheets. Food and Agriculture Organization of the United Nations. Retrieved 2007-11-20.
- ^ Nweeia, Martin T., et al.; Eichmiller, Frederick C.; Hauschka, Peter V.; Tyler, Ethan; Mead, James G.; Potter, Charles W.; Angnatsiak, David P.; Richard, Pierre R. et al. (2012). "Vestigial tooth anatomy and tusk nomenclature for Monodon monoceros". The Anatomical Record 295 (6): 1006–16. doi:10.1002/ar.22449. PMID 22467529.
- ^ Narwhal Whale Tusk. www.narwhalwhales.com. Retrieved on 2013-04-21.
- ^ Carwardine, Mark (1995). DK Handbooks: Whales Dolphins and Porpoises. Dorling Kindersley. ISBN 1-56458-620-0.
- ^ Silverman, H. B. and Dunbar, M. J. (1980). "Aggressive tusk use by the narwhal (Monodon monoceros L.)". Nature 284 (5751): 56–57. doi:10.1038/284057a0.
- ^ a b Broad, William (December 13, 2005). "It's Sensitive. Really.". The New York Times. mirror
- ^ a b c "The Biology and Ecology of Narwhals". National Oceanic and Atmospheric Administration. Retrieved 2009-01-15.
- ^ a b c Laidre, K.L. and Heide-Jørgensen, M. P. (2005). "Winter feeding intensity of narwhals". Marine Mammal Science 21 (1): 45–57. doi:10.1111/j.1748-7692.2005.tb01207.x.
- ^ ANIMAL BYTES – Narwhal. Seaworld.org. Retrieved on 2013-04-21.
- ^ Laidre, K. L.; Heide-Jørgensen, M. P.; Dietz, R.; Hobbs, R. C. and Jørgensen, O. A. (2003). "Deep-diving by narwhals, Monodon monoceros: differences in foraging behavior between wintering areas?". Marine Ecology Progress Series 261: 269–281. doi:10.3354/meps261269.
- ^ Borenstein, Seth (25 April 2008). "Narwhals more at risk to Arctic warming than polar bears". Associated Press. Retrieved 2008-04-27.
- ^ Bastian, Dawn E; Judy K. Mitchell (2004). Handbook of Native American Mythology. ABC-CLIO. pp. 54–55. ISBN 1-85109-533-0.
- ^ Daston, Lorraine and Katharine Park. Wonders and the Order of Nature, 1150–1750. New York: Zone Books, 2001.
- ^ Purchasing Power of British Pounds from 1264 to 2007. measuringworth.com
- ^ a b Shepard, Odell (1956). The Lore of the Unicorn. Harper and Row Publishers.
- ^ Melville, Herman (1851). Moby-Dick; or, The Whale. Harper and Brothers.
Further reading
 | Wikispecies has information related to: Monodon monoceros |
 | Wikimedia Commons has media related to: Monodon monoceros |
- M. P. Heide-Jorgensen. "Narwhal", in Encyclopedia of Marine Mammals, Perrin, Wursig and Thewissen eds. ISBN 0-12-551340-2
- Heide-Jørgensen, M. P. and K. L. Laidre (2006). Greenland’s Winter Whales: The beluga, the narwhal and the bowhead whale. Ilinniusiorfik Undervisningsmiddelforlag, Nuuk, Greenland. ISBN 978-87-7975-299-3.
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