Narwhal

This is a good article. Click here for more information.
Page semi-protected
Source: Wikipedia, the free encyclopedia.
For other uses, see Narwhal (disambiguation).

Narwhal
Temporal range: Quaternary–Present
↓
[1][2]
Diagram showing a narwhal and scuba diver from the side: the body of the whale is about three times longer than a human.
Size compared to an average human

Least Concern  (IUCN 3.1)[3]
CITES Appendix II (CITES)[4]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Monodontidae
Genus: Monodon
Linnaeus, 1758
Species:
M. monoceros
Binomial name
Monodon monoceros
Distribution of narwhal populations

The narwhal (Monodon monoceros), is a species of

pigmentation, with blackish-brown markings over a white background. An adult narwhal is typically 3.0 to 5.5 m (9.8 to 18.0 ft) in length and 800 to 1,600 kg (1,800 to 3,500 lb) in weight. Instead of a dorsal fin, it possesses a shallow dorsal ridge. Carl Linnaeus scientifically described the species in 1758 in his work Systema Naturae
.

The narwhal inhabits

cetaceans
, the narwhal uses clicks, whistles and knocks to communicate with others of its kind.

There are estimated to be 170,000 living narwhals, and the species is listed as

least concern by the International Union for Conservation of Nature. The narwhal has been hunted for hundreds of years by Inuit in northern Canada and Greenland for meat and ivory
 and a regulated subsistence hunt continues.

Taxonomy

The narwhal was one of many species originally described by Carl Linnaeus in his 1758 Systema Naturae.[5] An early 1555 drawing by Olaus Magnus depicts a fish-like creature with a horn on its forehead. He later assigned it to "Monocerote".[6] Its name comes from the Old Norse word nár, meaning "corpse," which possibly refers to the animal's gray, mottled skin[7] and its habit of remaining motionless at the water's surface, a behavior known as "logging" that usually happens in the summer.[8] The scientific name, Monodon monoceros, is derived from Greek: "single-tooth single-horn".[9]

The narwhal is most closely related to the

melons (acoustic sensory organs), short snouts and the absence of a true dorsal fin.[10][11]

Although the narwhal and beluga are classified as separate genera, there is some evidence that they may, very rarely,

interbreed. The remains of three animals were discovered, including one of an abnormal-looking whale, in West Greenland around 1990. The unusual whale was described by marine zoologists as unlike any known species, and it had features midway between a narwhal and a beluga, indicating that the remains belonged to a narluga (a hybrid between the two species);[12] in 2019, this was confirmed by DNA analysis.[13] Whether the hybrid could breed remains unknown.[14][12]

Evolution

Genetic evidence suggests that within the

million years ago (mya), the narwhal split from the beluga whale.[17] Analysis of Monodontidae fossils indicates that they had separated from Phocoenidae around 10.82 to 20.12 mya; they are considered to be a sister taxon.[18] The following phylogenetic tree is based on a 2019 study of the family Monodontidae.[19]

†Kentriodon pernix

Tursiops truncatus (Common bottlenose dolphin)

Phocoena phocoena (Harbour porpoise)

Monodontidae

†Haborodelphis japonicus

†Denebola brachycephala

†Bohaskaia monodontoides

Monodon monoceros

†

Casatia thermophila

IRSNB M 1922

Delphinapterus leucas (Beluga whale)

Description

Two narwhals at the water surface
Narwhals near the surface

The narwhal is a medium-sized whale, with a body length of 3.0 to 5.5 m (9.8 to 18.0 ft), excluding the tusk.[20][21] Males average 4.1 m (13 ft) in length, while females average 3.5 m (11 ft). Adults typically range between 800 to 1,600 kg (1,800 to 3,500 lb), with males outweighing their female counterparts.[20] Male narwhals attain sexual maturity at 11 to 13 years of age, reaching a length of 3.9 m (13 ft). Females become sexually mature at a younger age, between 5 and 8 years old, when they are about 3.4 metres (11 ft) long.[20]

The

vertebrae are jointed, like those of land mammals, instead of being fused together as in most whales, allowing a great range of neck flexibility. These characteristics are shared by the closely related beluga whale.[8] Male and female narwhals have different tail flukes; the former are bent inward, while the latter have a sweep-back on the front margins. This is thought to be an adaptation for reducing drag caused by the tusk.[21]

Compared with most other marine mammals, the narwhal has a higher amount of

slow-twitch, allowing for endurance and manoeuvrable motion.[25]

Tusk

The tusk of a male narwhal on display.
Narwhal tusk

The most conspicuous characteristic of the male narwhal is a single long tusk, which is a canine tooth[26] that projects from the left side of the upper jaw.[27] The tusk grows throughout the animal's life, reaching an average of 1.5 to 2.5 m (4.9 to 8.2 ft).[28][29] Tusks can sometimes reach lengths of up 3 m (9.8 ft).[30] It is hollow and weighs up to 7.45 kg (16.4 lb). Some males may grow two tusks, occurring when the right canine also protrudes through the lip.[31] Females rarely grow tusks: when they do, the tusks are typically smaller than those of males, with less noticeable spirals.[32][33]

The purpose of the narwhal tusk is debated. Some biologists suggest that narwhals use their tusks in fights, while others argue that their tusks may be of use in breaking sea ice or in finding food. Tusks are universally acknowledged to be

Arctic cod, making them easier to catch for feeding.[38][39] Females, who usually do not have tusks, live longer than males, hence the tusk cannot be essential to the animal's survival. It is generally accepted that the primary function of the narwhal tusk is associated with sexual selection.[40]

Vestigial teeth

The narwhal has several small vestigial teeth that reside in open tooth sockets which are situated in the upper jaw. These teeth, which differ in form and composition, encircle the exposed tooth sockets laterally, posteriorly, and ventrally.[26][41] The varied morphology and anatomy of small teeth indicate a path of evolutionary obsolescence.[26]

Distribution

Six narwhals near the water surface
Pod of narwhals

The narwhal is found predominantly in the Atlantic and Russian areas of the

Franz Joseph Land and Severnaya Zemlya.[7] The northernmost sightings of narwhals have occurred north of Franz Joseph Land, at about 85° North latitude.[7] There are an estimated 12,500 narwhals in northern Hudson Bay, whereas around 140,000 reside in Baffin Bay.[44]

Migration

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, often 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 in wider fractures known as leads.[45] As spring comes, these leads open up into channels and the narwhals return to the coastal bays.[46] Narwhals in the Baffin Bay typically travel further north, to northern Canada and Greenland, between June and September. After this period, they move south to the Davis Strait, a journey that spans around 1,700 kilometres (1,100 mi), and stay there until April.[44] Narwhals from Canada and West Greenland winter regularly visit the pack ice of the Davis Strait and Baffin Bay along the continental slope with less than 5% open water and high densities of Greenland halibut.[47]

Behaviour and ecology

Tail fluke of two narwhals
Narwhal tail fluke

Narwhals normally congregate in groups of five to ten—and sometimes up to twenty—individuals. 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.[20] In the summer, several groups come together, forming larger aggregations which can contain from 500 to over 1,000 individuals.[20] Bull narwhals have been observed rubbing each other's tusks, a display known as "tusking".[36][48]

When in their wintering waters, narwhals make some of the deepest dives recorded for a marine mammal, diving to at least 800 m (2,620 ft) over 15 times a day, with many dives reaching 1,500 m (4,920 ft). Dives to these depths last around 25 minutes.[49] Dive times can also vary in depth, based on local variation between environments, as well as seasonality. For example, in the Baffin Bay wintering grounds, they tend to dive deep within the precipitous coasts, typically south of Baffin Bay. This suggests differences in habitat structure, prey availability, or genetic adaptations between subpopulations. In the northern wintering grounds, narwhals do not dive as deep as the southern population, in spite of the greater water depths in these areas. This is mainly attributed to prey being concentrated nearer the surface, which causes narwhals to subsequently alter their foraging strategies.[49]

Diet

Compared with other marine mammals, narwhals have a relatively restricted and specialized diet.

wolffish, capelin, skate eggs and sometimes rocks.[20][47][45]

In

summer, they eat mostly Arctic cod and Greenland halibut, with other fish such as polar cod making up the remainder of their diet.[51] Narwhals consume much more food throughout the winter months than they do during the summer months.[47][45] Due to the lack of well-developed dentition, narwhals are believed to feed by swimming close to prey and then sucking it into the mouth.[52]

Breeding

Female narwhals start bearing calves when six to eight years old.[8] Adults mate from March to May when they are in the offshore pack ice. After a gestation of 15 months, females give birth to calves between July and August.[53] As with most marine mammals, only a single young is born, averaging 1.5 m (4.9 ft) in length. At birth, calves are white or light grey in colour.[54] The birth interval is typically between two and three years.[55] During summer population counts along different coastal inlets of Baffin Island, calf numbers varied from 0.05% to 5% of the total numbering from 10,000 to 35,000 narwhals, suggesting that higher calf counts may reflect calving and nursery habitats in favourable inlets.[56]

Newborn calves begin their lives with a thin layer of

mother's milk which is rich in fat. Calves are dependent on milk for around 20 months.[8] This long lactation period gives the calves time to learn skills they will need to survive as they mature. Calves typically stay within two body lengths of the mother.[8][56] The species is thought to go through menopause; during this phase, females may continue to take care of calves in the pod.[55]

In a 2024 study, scientists concluded that 5 species of Odontoceti evolved menopause to acquire higher overall longevity. Their reproductive lives on the other hand, did not increase or decrease. A few key reasons align for this, namely intergenerational assistance, in which reproductive and non-reproductive females play a role in the development of calves. It has been hypothesized that calves of the 5 Odontoceti species require the assistance of menopausal females to have an enhanced chance at survival, as they are extremely difficult for a single female to successfully rear.[57]

Communication

See also: Whale vocalization

Like most toothed whales, narwhals use sound to navigate and hunt for food. Narwhals primarily vocalise through "clicks", "whistles" and "knocks", created by air movement between chambers near the

melon, which can be controlled through surrounding musculature.[61] Echolocation clicks are used for detecting prey and locating barriers at short distances.[62] "Whistles" and "throbs" are mostly used to communicate with other pod members.[63] Calls recorded from the same pod are more similar than calls from different pods, suggesting the possibility of group- or individual-specific calls in narwhals. Narwhals sometimes adjust the duration and pitch of their pulsed calls to maximise sound propagation in varying acoustic environments.[64] Other sounds produced by narwhals include trumpeting and "squeaking-door sounds".[8] The narwhal vocal repertoire is similar to that of the closely related beluga, with comparable whistle frequency ranges, whistle duration and repetition rates of pulse calls, however beluga whistles are thought to have a higher frequency range and more diversified whistle contours.[65]

Longevity and mortality factors

scavenging
a narwhal carcass

Narwhals live an average of 50 years, however, age determination techniques using

freeze over in late autumn.[20][67] As narwhals breathe air, they drown if open water is no longer accessible and the ice is too thick for them to break through. Breathing holes in the ice may be up to 1,450 m (4,760 ft) apart, 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.[24] Narwhals also die of starvation from these entrapment events.[20]

In 1914–1915, around 600 narwhal carcasses were discovered after entrapment events, most occurring in areas such as

Arctic winter, including in some places where such events have never been recorded before.[67] This suggests later departure dates from summering grounds. Wind and currents move sea ice from adjacent locations to Greenland, leading to fluctuations in concentration. Due to their tendency of returning to the same areas, changes in weather and ice conditions are not always associated with narwhal movement toward open water. It is currently unclear to what extent sea ice changes pose a danger to narwhals.[20]

Major predators are

Orcas group together to overwhelm and surround narwhal pods,[70] killing up to dozens of narwhals in a single attack.[71] To escape predators such as orcas, narwhals may use prolonged submergence to hide under ice floes rather than relying on speed.[24]

Conservation

The narwhal is listed as

Inglefield Bredning and Melville Bay are 16,000, 8,000 and 3,000, respectively. There are roughly 837 narwhals in the waters off Svalbard.[3]

In 1972, the United States banned commercial imports of products made from narwhal body parts as stated by the

captivity.[36]

Threats

Data showing the number of caught belugas and narwhals
Beluga and narwhal catches

Narwhals are hunted for their skin, meat, teeth, tusks, and carved vertebrae, which are commercially traded. About 1,000 narwhals are killed per year: 600 in Canada and 400 in Greenland. Canadian harvests were steady at this level in the 1970s, dropped to 300–400 per year in the late 1980s and 1990s and have risen again since 1999. Greenland harvested more, 700–900 per year, in the 1980s and 1990s.[73]

Narwhal tusks are sold both carved and uncarved in Canada

economic analysis noted that whale watching may be an alternate source of revenue.[74]

A man holding the head of a dead narwhal
Hunter posing next to a narwhal head (1903)

As narwhals grow,

mercury were not nearly as abundant. A study found that the blubber was nearly devoid of these metals, whereas the liver and kidneys had a dense concentration of these metals. Individuals of different weight and sex showed dissimilarities in the concentration of metals in their organs.[77]

Narwhals are one of the most vulnerable Arctic marine mammals to

glacials and climate change.[80]

Reduction in sea ice has possibly led to increased exposure to predation. In 2002, hunters in

oil exploration disrupt the normal migration patterns. These disturbed migrations may also be associated with increased sea ice entrapment.[82]

Relationship with humans

Inuit

Inuit lance head made from narwhal tusk with a meteorite-iron point
The head of an Inuit lance made from a narwhal tusk, with a meteorite-iron point (British Museum)

While it is generally illegal to hunt narwhals,

hunting rifles are used.[7]

In Inuit legend, the narwhal's tusk was created when a woman with harpoon rope tied around her waist was dragged into the ocean after the harpoon had stuck into a large narwhal. She was then transformed into a narwhal; her hair, which she was wearing in a twisted knot, became the spiraling narwhal tusk.[84]

Alicorn

Main article: Unicorn horn

The narwhal tusk has been highly sought-after in Europe for centuries. This stems from a medieval belief that narwhal tusks were the horns of the legendary unicorn.[85][86] Trade of narwhal tusks approximately began in 1000.[87] Scientists have long speculated that Vikings collected tusks washed ashore on beaches of Greenland and surrounding areas, yet others predict Norsemen interchanged tusks with Europeans after acquiring them from Inuit. Tusks spread across the Middle East and East Asia. A hypothesis suggests that Norsemen may have hunted narwhals, though this was never confirmed and was later disproven.[88][89] Vikings made weapons out of tusks to be used in battles or hunts. Hadley Meares, a historian, stated, "The trade strengthened during the Middle Ages, when the unicorn became a symbol of Christ, and therefore an almost holy animal."[90] The trade became prevalent in Renaissance times.[91]

Across Europe, narwhal tusks were given as state gifts to kings and queens, in addition to a growing demand for the supposed powers of unicorn horns.

measles, fevers, and pain.[97][98] The rise of science towards the end of the 17th century led to a decreased belief in magic and alchemy. After it was determined that narwhal tusks were not effective antidotes, the practice of using them for this purpose was subsequently abandoned.[99]

See also

References

  1. doi:10.5962/bhl.title.57425
    .
  2. ^ "Monodon monoceros Linnaeus 1758 (narhwal)". PBDB.org. Archived from the original on 12 July 2020. Retrieved 11 July 2020.
  3. ^
    doi:10.2305/IUCN.UK.2017-3.RLTS.T13704A50367651.en
    .
  4. ^ a b "Appendices | CITES". cites.org. Archived from the original on 5 December 2017. Retrieved 14 January 2022.
  5. ^ Linnaeus, Carl (1758). "Monodon monoceros". Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata (in Latin). Stockholm: Lars Salvius. p. 824.
  6. ISBN 978-0-295-80469-9
    .
  7. ^
    ISBN 87-7975-299-3
    .
  8. ^ a b c d e f "The narwhal: unicorn of the seas" (PDF). Fisheries and Oceans Canada. 2007. Archived (PDF) from the original on 10 July 2013. Retrieved 10 July 2013.
  9. ^ Webster, Noah (1880). "Narwhal". An American Dictionary of the English Language. G. & C. Merriam. p. 854.
  10. ISBN 0-87196-871-1
    .
  11. ISBN 0-8018-8221-4
    .
  12. ^
    ISSN 0824-0469
    .
  13. PMID 31221994
    .
  14. ^ Pappas, Stephanie (20 June 2019). "First-ever beluga–narwhal hybrid found in the Arctic". Live Science. Archived from the original on 20 June 2019. Retrieved 20 June 2019.
  15. PMID 10837160
    .
  16. S2CID 55606151
    .
  17. PMID 32315590
    .
  18. PMID 30033539
    .
  19. S2CID 202018525
    . Retrieved 21 January 2024.
  20. ^
    ISBN 0-691-09160-9. Archived
    from the original on 28 January 2024. Retrieved 27 January 2024.
  21. ^
    ISSN 0824-0469
    .
  22. ^ "Monodon monoceros". Fisheries and Aquaculture Department: Species Fact Sheets. Food and Agriculture Organization of the United Nations. Archived from the original on 16 February 2012. Retrieved 20 November 2007.
  23. PMID 18021441
    .
  24. ^
    ISSN 0824-0469
    .
  25. PMID 33627459
    .
  26. ^
    PMID 24639076. Archived
    from the original on 24 January 2024. Retrieved 24 January 2024.
  27. PMID 33972883
    .
  28. PMID 33705717. Archived
    from the original on 26 January 2024. Retrieved 26 January 2024.
  29. ISBN 0-226-50341-0. Archived
    from the original on 28 January 2024. Retrieved 28 January 2024.
  30. ISBN 978-0-691-23244-7. Archived
    from the original on 28 January 2024. Retrieved 28 January 2024.
  31. ISSN 1751-8369
    .
  32. PMID 34347780
    .
  33. S2CID 40943163. Archived
    from the original on 20 June 2022. Retrieved 26 January 2024.
  34. ISSN 0008-4301. Archived
    from the original on 25 July 2019. Retrieved 23 January 2024.
  35. PMID 24639076
    .
  36. ^ a b c Broad, William (13 December 2005). "It's sensitive. Really". The New York Times. Archived from the original on 28 January 2024. Retrieved 22 February 2017.
  37. Independent.co.uk. Archived
    from the original on 18 June 2022. Retrieved 31 March 2014.
  38. PMID 27784729
    .
  39. ISBN 978-0-691-23664-3
    .
  40. ISSN 0824-0469
    .
  41. ^ "For a dentist, the narwhal's smile is a mystery of evolution". Smithsonian Insider. 18 April 2012. Archived from the original on 14 September 2016. Retrieved 6 September 2016.
  42. ISBN 978-0-12-804327-1, archived
    from the original on 20 January 2023, retrieved 27 January 2024
  43. ISSN 2309-2491. Archived
    from the original on 27 January 2024. Retrieved 27 January 2024.
  44. ^
    ISSN 0008-4301. Archived
    from the original on 28 January 2024. Retrieved 20 January 2024.
  45. ^
    ISSN 0824-0469
    .
  46. ^
    PMID 18494365
    .
  47. ^
    ISSN 1095-9289
    .
  48. ^ "The biology and ecology of narwhals". noaa.gov. National Oceanic and Atmospheric Administration. Archived from the original on 14 August 2022. Retrieved 15 January 2009.
  49. ^
    ISSN 0171-8630
    .
  50. PMID 33122802
    .
  51. ^
    ISSN 0008-4301
    .
  52. ISSN 2050-3385
    .
  53. ISBN 2-88032-936-1. Archived
    from the original on 28 January 2024. Retrieved 28 January 2024.
  54. ISBN 0-935848-47-9. Archived
    from the original on 28 January 2024. Retrieved 28 January 2024.
  55. ^
    ISSN 0022-2372. Archived
    from the original on 28 January 2024. Retrieved 22 January 2024.
  56. ^ a b Evans Ogden, Lesley (6 January 2016). "Elusive narwhal babies spotted gathering at Canadian nursery". New Scientist. Archived from the original on 21 September 2016. Retrieved 6 September 2016.
  57. PMID 38480878
    .
  58. PMID 29897955
    .
  59. ISBN 978-0-691-19062-4. Archived
    from the original on 28 January 2024. Retrieved 28 January 2024.
  60. S2CID 85148204. Archived
    from the original on 5 October 2022. Retrieved 27 January 2024.
  61. ISSN 2071-1050
    .
  62. PMID 34772963
    .
  63. ISSN 0824-0469
    .
  64. ISSN 0824-0469
    .
  65. S2CID 246176509
    .
  66. ISSN 0022-2372
    .
  67. ^
    S2CID 253807718
    .
  68. JSTOR 207815
    .
  69. ISBN 978-0-08-091993-5. Archived
    from the original on 28 January 2024. Retrieved 18 November 2020.
  70. PMID 22520955
    .
  71. ^ "Invasion of the killer whales: killer whales attack pod of narwhal". Public Broadcasting System. 19 November 2014. Archived from the original on 22 October 2016. Retrieved 23 October 2016.
  72. ^ "Fact sheet narwhal and climate change| CITES" (PDF). cms.int. Archived (PDF) from the original on 26 January 2024. Retrieved 21 January 2024.
  73. S2CID 89062294
    , retrieved 14 February 2024
  74. ^
    ISSN 0004-0843
    .
  75. ^ Greenfieldboyce, Nell (19 August 2009). "Inuit hunters help scientists track narwhals". NPR.org. National Public Radio. Archived from the original on 24 October 2016. Retrieved 24 October 2016.
  76. ^
    ISSN 0106-1054
    .
  77. ^
    ISSN 0706-652X
    .
  78. ISBN 978-0-429-21746-3
    , retrieved 4 February 2024
  79. ^
    ISSN 0171-8630
    .
  80. ISSN 0006-3207
    .
  81. ISSN 1751-8369
    .
  82. ISSN 0006-3207
    .
  83. ISSN 2296-7745
    .
  84. ISBN 1-85109-533-0
    .
  85. ^
    S2CID 162878182
    .
  86. ISBN 0-942299-91-4
    .
  87. S2CID 10030083
    .
  88. S2CID 135259639
    .
  89. ISSN 2571-9408
    .
  90. ^ Berger, Miriam (30 November 2019). "The narwhal tusk has a wondrous and mystical history. A new chapter was added on London Bridge". The Washington Post. Retrieved 18 February 2024.
  91. ISSN 0004-3079
    .
  92. PMID 38358838
    .
  93. ISBN 978-1-317-45938-5. Archived
    from the original on 28 September 2023. Retrieved 18 September 2023.
  94. ISBN 978-1-84893-270-8
    , retrieved 13 February 2024
  95. S2CID 133366872
    .
  96. ISBN 978-0-12-809559-1
    .
  97. ISBN 978-2-88295-400-8
    .
  98. PMID 33944492
    .
  99. ^ Meares, Hadley (16 April 2019). "How 'unicorn horns' became the poison antidote of choice for paranoid royals". HISTORY. Retrieved 8 March 2024.

Further reading

Retrieved from "https://en.wikipedia.org/w/index.php?title=Narwhal&oldid=1220065384"