Mammal Species of the World
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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.
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 )
The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states.
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Regularity: Regularly occurring
Type of Residency: Year-round
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).
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
Length: 500 cm
Weight: 1600000 grams
Size in North America
Average: 4.7 m males; 4.1 m females
Average: 1,580 kg males; 960 kg females
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
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).
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).
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).
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 )
Comments: Known prey includes squid, polar cod, demersal fishes, and crustaceans (Leatherwood and Reeves 1983).
Narwhals harbour several species of commensal animals such as whale lice and certain nematodes. They act to limit the populations of their prey species.
- Whale lice
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.
- killer whales (Orcinus orca)
- Greenland sharks (Somniosus microcephalus)
- polar bears (Ursus maritimus)
- humans (Homo sapiens)
This list may not be complete but is based on published studies.
Known prey organisms
Based on studies in:
Canada, high Arctic (Ice cap)
This list may not be complete but is based on published studies.
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).
Large aggregations sometimes observed; these are subdivided into cohesive units of 20 or fewer individuals. Different sexes and ages may segregate or mix.
Life History and Behavior
Perception Channels: tactile ; chemical
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).
Status: wild: 30 to 55 years.
Status: captivity: 1 to 4 months.
Status: wild: 40.0 years.
Lifespan, longevity, and ageing
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
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.
Evolution and Systematics
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.
Molecular Biology and Genetics
Barcode data: Monodon monoceros
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
Statistics of barcoding coverage: Monodon monoceros
Public Records: 2
Specimens with Barcodes: 15
Species With Barcodes: 1
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
IUCN Red List Assessment
Red List Category
Red List Criteria
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.
- 1996Data Deficient(Baillie and Groombridge 1996)
- 1996Data Deficient
- 1994Insufficiently Known(Groombridge 1994)
- 1990Insufficiently Known(IUCN 1990)
- 1988Insufficiently Known(IUCN Conservation Monitoring Centre 1988)
National NatureServe Conservation Status
Rounded National Status Rank: N3 - Vulnerable
Rounded National Status Rank: NU - Unrankable
NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
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.
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).
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).
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.
Needs: See IUCN (1991) for a discussion of conservation measures.
Relevance to Humans and Ecosystems
There are no known adverse affects to humans.
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
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.
IUCN Red List Category
The narwhal, or narwhale (Monodon monoceros), is a medium-sized toothed whale and the animal with the largest canines. It lives year-round in the Arctic. It is one of two living species of whale in the Monodontidae family, along with the beluga whale. The narwhal males are distinguished by a long, straight, helical tusk, which is an elongated upper left canine. It was one of many species described by Carolus Linnaeus in his publication Systema Naturae in 1758.
Like the beluga, narwhals are medium-sized whales. For both genders, including the male's tusk, the total body size can range from 3.95 to 5.5 metres (13.0 to 18.0 feet); the males are slightly larger than the females. The average weight of an adult narwhal is 800 to 1,600 kilograms (1,800 to 3,500 pounds). At around 11 to 13 years old, the males become sexually mature; females become sexually mature at about 5 to 8 years old. Narwhals do not have a dorsal fin, and their neck vertebrae are jointed like those of other mammals, not fused as in dolphins and most whales.
Found primarily in Canadian Arctic and Greenlandic waters, the narwhal is a uniquely specialized Arctic predator. In winter, it feeds on benthic prey, mostly flatfish, at depths of up to 1500 m under dense pack ice. During the summer, narwhals mostly eat Arctic cod and Greenland halibut, with other fish such as Polar cod making up the minority of their diet. Each year, they migrate from bays into the ocean as summer comes. In the winter, the male narwhals occasionally dive up to 1,500 metres (4,900 feet) in depth, with dives lasting up to 25 minutes. Narwhals, like most toothed whales, communicate with "clicks", "whistles", and "knocks".
Narwhals can live up to 50 years old. They are often killed when the sea ice freezes over and they cannot breathe. Another cause of fatality, specifically among young whales, is starvation. The current population of the narwhal is about 75,000, so narwhals qualify for Near Threatened under the criterion of the International Union for Conservation of Nature (IUCN). 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.
Taxonomy and etymology
The narwhal was one of the many species originally described by Linnaeus in his Systema Naturae. 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 and its summer-time habit of lying still at or near the surface of the sea (called "logging"). The scientific name, Monodon monoceros, is derived from the Greek: "one-tooth one-horn".
The narwhal is most closely related to the beluga whale. Together, these two species comprise the only extant members of the family Monodontidae, sometimes referred to as the "white whales". The Monodontidae are distinguished by medium size (at around 4 m (13 ft) in length), forehead melons (round sensory organs), short snouts, and the absence of a true dorsal fin. The white whales, dolphins (Delphinidae) and porpoises (Phocoenidae) together comprise the superfamily Delphinoidea, 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 rest of Delphinoidea within the past 11 million years. Fossil evidence shows that ancient white whales lived in tropical waters. They may have migrated to Arctic and sub-Arctic waters in response to changes in the marine food chain during the Pliocene.
Narwhals are medium-sized whales, and are 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). Males, at an average length of 4.1 m (13 ft 5 in), are slightly larger than females, with an average length of 3.5 m (11 ft 6 in). Typical adult body weight ranges from 800 to 1,600 kg (1,800 to 3,500 lb). Males attain sexual maturity at 11 to 13 years of age, when they are 3.9 m (12 ft 10 in) long, and females at 5 to 8 years old, when they are 3.4 m (11 ft 2 in) long. The pigmentation of narwhals is a mottled pattern, with blackish-brown markings over a white background. They are darkest when born and become whiter with age; white patches develop on the navel and genital slit at sexual maturity. Old males may be almost pure white. Narwhals do not have a dorsal fin, possibly an evolutionary adaptation to swimming easily under ice. Their neck vertebrae are jointed, like those of land mammals, instead of being fused together as in most whales. Both these characteristics are shared by the beluga whale. The tail flukes of female narwhals have front edges that are swept back, and those of males have front edges that are more concave and lack a sweep-back. This is thought to be an adaptation for reducing drag caused by the tusk.
The most conspicuous characteristic of the male narwhals are their single extremely long tusk, a canine tooth that projects from the left side of the upper jaw, through the lip and forms a left-handed helix spiral. Their tusks grow throughout life, reaching lengths from about 1.5 to 3.1 m (4 ft 11 in to 10 ft 2 in). It is hollow and weighs 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 through the lip. Females sometimes grow tusks; although only about 15 percent of females have a tusk and female tusks are smaller than those of males, with a less noticeable spiral. Females may produce a second tusk, but there is only a single recorded case of such happening. The tusks are surrounded posteriorly, ventrally, and laterally by several small teeth which vary in morphology and histology. These teeth are vestigial and never erupt, and the narwhal's mouth usually appears toothless.
Biology traditionally considers the tusk a secondary sexual characteristic, similar to the mane of a lion or the tail feathers of a peacock. 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, other aggressive behaviours, or for breaking sea ice in their Arctic habitat. Some evidence suggests that the tusk is an innervated sensory organ. However, this idea doesn't explain why females don't grow large tusks as well. There is at least one recorded case of a tusk being used against another species. A broken tusk was found embedded in the melon of a beluga, suggesting a fight.
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. The northernmost sightings of narwhal have occurred north of Franz Joseph Land, at about 85° North latitude. Most of the world's narwhals are concentrated in the fjords and inlets of Northern Canada and western Greenland. They are able to survive in depths of up to 1,500 m (4,900 ft) below sea level.
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. As spring comes, these leads open up into channels and the narwhals return to the coastal bays. 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. Feeding in the winter accounts for a much larger portion of narwhal energy intake than in the summer.
Narwhals normally congregate in groups of about five to ten, and 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"), but mixed groups can occur at any time of year. In the summer, several groups come together, forming larger aggregations which can contain from 500 to over 1000 individuals. At times, bull narwhals rub their tusks together, which is known as "tusking". This is thought to maintain social dominance hierarchies or maintenance of the tusk as a sensitive sensory organ.
Narwhals have a relatively restricted and specialized diet. Their prey is predominantly composed of Greenland halibut, polar and Arctic cod, cuttlefish, shrimp and armhook squid. Additional items found in stomachs have included wolffish, capelin, skate eggs and sometimes rocks, accidentally ingested when whales feed near the bottom. 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, which have similarly reduced dentition, also suck up their prey.
Narwhals have a very intense summer feeding society. One study published in the Canadian Journal of Zoology tested 73 narwhals of different age and gender to see what they ate. The individuals were from the Pond Inlet and had their stomach contents tested from June 1978 until September 1979. The study found in 1978 that the Arctic cod (Boreogadus saida) made up about 51% of the diet of the narwhals, with the next most common animal being the Greenland halibut (Reinhardtius hippoglossoides), consisting of 37% of the weight of their diet. A year later, the percentages of both animals in the diet of narwhals had changed. Arctic cod represented 57%, and Greenland halibut 29% in 1979. The deep-water fish - halibut, redfish (Sebastes marinus), and polar cod (Arctogadus glacialis) - are found in the diet of the males, which means that the narwhals can dive deeper than 500 m (1,600 ft) below sea level. The study found that the dietary needs of the narwhal did not differ among genders or ages.
When in their wintering waters, narwhals make some of the deepest dives recorded for a marine mammal, diving to at least 800 metres (2,600 feet) over 15 times per day, with many dives reaching 1,500 metres (4,900 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.
As with most toothed whales, narwhals use sound to navigate and hunt for food. "Clicks", "whistles" and "knocks", may be created via air between chambers near the blow-hole, and reflected off the sloping front of the skull. These sounds are then focused by the animal's melon, which can be controlled by musculature. "Click trains" are produced both for echo-location of prey, and for locating obstacles at short distances. It is possible that individual "bangs" are capable of disorienting or incapacitating prey, making them easier to hunt, but this has not been verified. The whistles of a narwhal are rarely heard, especially compared to the beluga. Other sounds produced by narwhals include trumpeting and squeaking door sounds.
Breeding and early life
Females start bearing calves when six to eight years old. Adult narwhals mate in April or May when they are in the offshore pack ice. Gestation lasts for 14 months and calves are born between June and August the following year. As with most marine mammals, only a single young is born. Newborn calves average 1.6 metres (5.2 feet) in length and are dark grey. The newborn calves begin their lives with a thin layer of blubber which thickens as they nurse their mother's milk which is rich in fat. Calves are dependent on milk for around 20 months. This long lactation period gives calves time to learn the skills they need for survival. Mothers and calves stay close and when travelling, the calf stays by its mother's back for assistance in swimming.
Life span and mortality
Narwhals can live up to at least 50 years. Almost all modern predation of narwhals is by humans; other predators are polar bears, which attempt to swipe narwhals at breathing holes and mainly target young whales, and killer whales (orcas) which can group together to overwhelm a single narwhal. Greenland sharks and walruses may take a few small young or weak and wounded adults, though this is likely quite rare. When it comes to escaping predators such as orcas, narwhals typically use prolonged submergence to hide under the ice rather than relying on speed.
Mortality often occurs when the narwhals suffocate after they fail to leave before the surface of the Arctic waters freeze over in the late autumn. Open water is formed in ice-covered water by fracturing events induced by strong winds, but when these conditions are absent ice can quickly form. The last major entrapment events occurred when there was little to no wind. Narwhals are mammals and need air to breathe, so when open water is no longer accessible and the ice is too thick for them to break through, they can drown. Maximum aerobic swimming distance between breathing holes in ice is less than 1,450 m (4,760 ft) which limits the use of foraging grounds and these holes must be at least 0.5 m (1.6 ft) wide to allow an adult whale to breathe. The events can trap groups as large as 600 individuals. Most entrapment events occur in narwhal wintering areas such as Disko Bay. In the largest entrapment in 1915 in West Greenland, over 1,000 narwhals were trapped under the ice. Despite the decreases in sea ice cover, there were several large cases of sea ice entrapment in 2008–2010 in the winter close to known summering grounds, two of which were locations where there had been no previous cases documented. This suggests later departure dates from summering grounds. Sites surrounding Greenland experience advection (moving) of sea ice from surrounding regions by wind and currents, increasing the variability of sea ice concentration. Due to strong site fidelity, changes in weather and ice conditions are not always associated with narwhal movement toward open water and therefore more data is needed to determine how vulnerable narwhals are to future sea ice changes. Narwhals can also die of starvation, especially the young.
Narwhals are one of many mammals that are being threatened by human actions. The world population of narwhals is currently estimated to be around 75,000. They are considered to be near threatened and several sub-populations have evidence of decline. In an effort to support conservation, the European Union established an import ban on tusks. Many other countries have quotas on catches, which will be important also in newly opening areas caused by decreasing sea ice cover. Narwhals are difficult to keep in captivity.
Inuit people, who call a tusked narwhal qilalugaq tugaalik, are allowed to hunt this whale species legally for subsistence. Narwhals have been extensively hunted the same way as other sea mammals, such as seals and whales, for its large quantities of fat which are one of the most important resources of the native people 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. 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.
During growth, the narwhal accumulates metals in its internal organs. One study found that many metals are low in concentration in the blubber of narwhals, and high in the liver and the kidney. Zinc and cadmium are found in higher densities in the kidney than the liver, and lead, copper and mercury were found to be the opposite. Certain metals were correlated with size and sex. During growth, it was found that mercury accumulated in the liver, kidney, muscle and blubber, and that cadmium settled in the blubber.
Narwhals are one of the most vulnerable Arctic marine mammals to climate change due to altering sea ice coverage in their environment, especially in their northern wintering grounds such as the Baffin Bay and Davis Strait regions. Satellite data collected from these areas shows the amount of sea ice has been markedly reduced. Narwhals' ranges for foraging are believed to be patterns developed early in their life which increase their ability to gain necessary food resources during winter. This strategy focuses on strong site fidelity rather than individual level responses to local prey distribution and this results in focal foraging areas during the winter. As such, despite changing conditions narwhals will continue returning to the same areas during migration. Despite its vulnerability to sea ice change, the narwhal has some flexibility when it comes to sea ice and habitat selection. It evolved in the late Pliocene, and so is moderately accustomed to periods of glaciation and environmental variability.
An indirect danger for narwhals associated with changes in sea ice is the increased exposure in open water. In 2002 there was an increase in narwhal catches by hunters in Siorapaluk that did not appear to be associated with increased effort, implying that climate change may be making the narwhal more vulnerable to harvesting. Scientists urge assessment of population numbers with the assignment of sustainable quotas for stocks and the collaboration of management agreements to ensure local acceptance. Seismic surveys associated with oil exploration have also disrupted normal migration patterns which may also be associated with increased sea ice entrapment.
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, and her hair, which she was wearing in a twisted knot, became the characteristic spiral narwhal tusk.
Some medieval Europeans believed narwhal tusks to be the horns from the legendary unicorn. As these horns were considered to have magic powers, such as neutralising poison and curing 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 bejewelled narwhal tusk for £10,000—the cost of a castle (approximately £1.5–2.5 million in 2007, using the retail price index). The tusks were staples of the cabinet of curiosities. Knowledge 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".
In literature and art
The narwhal was one of two possible explanations of the giant sea phenomenon written by Jules Verne in his 1870 novel Twenty Thousand Leagues Under the Sea. Verne thought that it would be unlikely that there was such a gigantic narwhal in existence. The size of the narwhal, or "unicorn of the see", as found by Verne, would have been 18 m (60 ft). For the narwhal to have caused the phenomenon, Verne stated that its size and strength would have to increase by five or ten times.
Herman Melville wrote a section on the narwhal (written as "narwhale") in his 1851 novel 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. Another claim made by him was that the Danish kings made their thrones from narwhal tusks.
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