page_title: Narwhal
section_title: Life span and mortality
hierarchical_section_title: Narwhal / Behaviour / Life span and mortality
caption_attribution_description: English: Scavenging: a polar bear (Ursus maritimus) eating flesh from a narwhal whale carcass (Monodon monoceros) (Photo: Jeff W. Higdon/DFO). doi:10.1371/journal.pone.0060797.g001
context_page_description: The narwhal or narwhale is a medium-sized toothed whale that possesses a large "tusk" from a protruding canine tooth. It lives year-round in the Arctic waters around Greenland, Canada, and Russia. It is one of two living species of whale in the family Monodontidae, along with the beluga whale. The narwhal males are distinguished by a long, straight, helical tusk, which is an elongated upper left canine. The narwhal was one of many species described by Carl Linnaeus in his publication Systema Naturae in 1758.
  Like the beluga, narwhals are medium-sized whales. For both sexes, excluding the male's tusk, the total body size can range from 3.95 to 5.5 m; the males are slightly larger than the females. The average weight of an adult narwhal is 800 to 1,600 kg. 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 most other mammals, not fused as in dolphins and most whales.
  Found primarily in Canadian Arctic and Greenlandic and Russian waters, the narwhal is a uniquely specialized Arctic predator.
context_section_description: Narwhals can live an average of 50 years, however research using aspartic acid racemization from the lens of the eyes suggests that narwhals can live to be as old as 115 ± 10 years and 84 ± 9 years for females and males, respectively  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. As narwhals need to breathe, they drown if open water is no longer accessible and the ice is too thick for them to break through. 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 last major entrapment events occurred when there was little to no wind. Entrapment can affect as many as 600 individuals, most occurring 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. More information is needed to determine the vulnerability of narwhals to sea ice changes. Narwhals can also die of starvation.
caption: A polar bear scavenging a narwhal carcass
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