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information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Narwhal (Monodon monoceros)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.

Summary

Description

The narwhal is a relatively small whale, famous for its unicorn-like tusk. It has a small bulbous head, reaches up to 4 m to 5 m in length and weighs up to 1600 kg. There is no dorsal fin but a small dorsal ridge. It has two blunt flippers and the tail ends with a left and right fluke. Body colouration varies with age. The young are generally grey all over until they develop dark spots or smears on their back and sides during maturity. At old age, spots become less apparent and the body can appear almost entirely white, especially in adult males.  The narwhal has only two horizontal teeth. In males, the left tooth commonly protrudes from the jaw to form a tusk that can reach 3 m in length. The protrusion of both teeth, forming tusks, in males has been recorded but protrusion in females is rare and teeth remain embedded.

Recorded distribution in Britain and Ireland

Monodon monoceros is probably an occasional visitor (vagrant) to the waters of British and Ireland.

Global distribution

Recorded in Arctic waters year-round from the central Canadian Arctic, Greenland and the central Russian Arctic. The majority of narwhal (Monodon monoceros) are recorded in Baffin Bay in winter months, which is east of Baffin Island and west of Greenland.

Habitat

The narwhal is a neritic and oceanic species. It is known to migrate seasonally. In winter months aggregations can be observed in offshore water covered in ice whereas, in summer months aggregations can be located in cold coastal areas.

Depth range

0-1500 m

Identifying features

  • Relatively small reaching 4 m to four 5 m in length.
  • Small bulbous head with little or no beak.
  • No dorsal fin but a small dorsal ridge.
  • Short blunt flippers.
  • Dark spots or smears on the back and sides (that depend on age).
  • Protrusion of a tooth (the tusk) from the jaw in males reaching up to 3 m long.

Additional information

The function of the tusk of Monodon monoceros is debated. Tusks are thought to be used in male-on-male competition for females and research suggests tusk scars inflicted by fights can be a sign of male dominance and is a foundation for establishing social male hierarchy (MacLeod, 1998). However, tusks may be used in sensory detection for food or identifying the location of females (Nweeia et al., 2014).

As Monodon monoceros is strongly associated with sea ice it is extremely vulnerable to climate change.  As the Earth begins to warm and Arctic sea ice retreats, Monodon monoceros habitat is set to shrink, which will push populations further north or cause local extinction (Chambault et al., 2017). Research suggests that warming can also reduce the use of ice as a barrier to open water predators such as the killer whale (Orcinus orca). As sea ice melts predators arrive earlier to summer grounds, which has the potential to change Monodon monoceros distribution and behaviour (Breed et al., 2017).

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Bibliography

  1. Heide-Jørgensen, M.P., Richard, P.R., Dietz, R. & Laidre, K.L., 2013. A metapopulation model for Canadian and West Greenland narwhals. Animal Conservation, 16 (3), 331-343. DOI https://doi.org/10.1111/acv.12000

  2. Breed, G.A., Matthews, C.J.D., Marcoux, M., Higdon, J.W., LeBlanc, B., Petersen, S.D., Orr, J., Reinhart, N.R. & Ferguson, S.H., 2017. Sustained disruption of narwhal habitat use and behavior in the presence of Arctic killer whales. Proceedings of the National Academy of Sciences, 114 (10), 2628-2633. DOI https://doi.org/10.1073/pnas.1611707114
  3. Chambault, P., Tervo, O.M., Garde, E., Hansen, R.G., Blackwell, S.B., Williams, T.M., Dietz, R., Albertsen, C.M., Laidre, K.L., Nielsen, N.H., Richard, P., Sinding, M.H.S., Schmidt, H.C. & Heide-Jørgensen, M.P., 2020. The impact of rising sea temperatures on an Arctic top predator, the narwhal. Scientific Reports, 10 (1). DOI https://doi.org/10.1038/s41598-020-75658-6
  4. Heide-Jørgensen, M.P., 2018. Narwhal: Monodon monoceros. In Bernd Würsig, J.G.M., Thewissen & K, M. Kovacs (eds). Encyclopedia of Marine Mammals (Third Edition): Academic Press, pp. 627-631.
  5. Jefferson, T.A., Webber, M.A. & Pitman, R.L., 2008. Marine Mammals of the World. A comprehensive guide to their identification. San Diego, California: Academic Press.
  6. Leatherwood, S., Caldwell, D.K., Winn, H.E., Schevill, W.E. & Caldwell, M.C., 1976. Whales, dolphins, and porpoises of the western North Atlantic: a guide to their identification. NOAA Technical Report NMFS Circular, Seattle.
  7. Lowry, L., Laidre, K. & Reeves, R., 2017. Monodon monoceros. The IUCN Red List of Threatened Species 2017: e.T13704A50367651. Available from: https://www.iucnredlist.org/species/13704/50367651
  8. MacLeod, C.D., 1998. Intraspecific scarring in odontocete cetaceans: an indicator of male ‘quality’ in aggressive social interactions? Journal of Zoology, 244 (1), 71-77. DOI https://doi.org/10.1111/j.1469-7998.1998.tb00008.x
  9. Nweeia, M.T., Eichmiller, F.C., Hauschka, P.V., Donahue, G.A., Orr, J.R., Ferguson, S.H., Watt, C.A., Mead, J.G., Potter, C.W., Dietz, R., Giuseppetti, A.A., Black, S.R., Trachtenberg, A.J. & Kuo, W.P., 2014. Sensory ability in the narwhal tooth organ system. The Anatomical Record, 297 (4), 599-617. DOI https://doi.org/10.1002/ar.22886

Datasets

  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biogeographic Information System),  2021. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2021-07-26

Citation

This review can be cited as:

Nash, R.A., 2021. Monodon monoceros Narwhal. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 26-07-2021]. Available from: https://www.marlin.ac.uk/species/detail/2331

Last Updated: 29/01/2021