Narwhals are a kind of toothed whale characterised by their straight and long tusk (horn) that rises from the upper left jaw. Found primarily in Canadian Arctic and Greenlandic waters , 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. Narwhal have been harvested for over a thousand years by Inuit people in Northern Canada and Greenland for their meat and the ivory of the tusk,  and a regulated subsistence hunt continues to this day. While populations appear stable, the narwhal has been deemed particularly vulnerable to climate change due to a narrow geographical range and specialized diet. However, the world population is currently estimated to be around 75,000 individuals. Apart from that, very little more is known about this rarely observed whale and there are few images of alive specimens.

Here there are their physical adaptations to the environment:

  • Lack of a dorsal fin: enables them to swim beneath ice to hide from their main predator, the killer whale. But this has an important disadvantage, that they can´t swim fastly. This is an “survival of the fittest” adaptation: narwhals that couldn´t hide below ice probably have been hunted by killer whales.
  • Very flexible neck: for scaning in a better way the deep waters of the Arctic, and so for capturing more prey. It´s an “struggle for existence” adaptation, abecause narwhals able to hunt and nourish succesfully have more chances to survive and reproduce.
  • Thick layer of blubber (whale fat): to retain heat to survive in the freezing waters of the North. It can be classified as an adaptation to the environment.
  • Higher range of echo location: to communicate through water from  further distances than normal whales.
  • Tusk: is traversed by up to 10 million nerve pathways. Scientists believe that they use it to make holes in sea ice to determine its thickness, to sense underwater pressures and temperatures and also as a special antenna to navigate by echolocation. Moreover, it´s thought to be a secondary sexual characteristic, as for example the feathers on the tail of peacocks.

This strange double toothed narwhal skull is exposed in the Zoologisches Museum, Hamburg.

narwalschaedel

  • NATURAL SELECTION:

Over-production: a narwhal´s life expectancy is around 50 years. Gestation is thought to last from 14 to 15 months and, except in very few occasions, a single calf is born.

Struggle for existence: narwhals diet is quite restricted and specific. Unlike their relative, the beluga whale, they don´t “eat what they find”. Their prey is predominantly composed of Greenland halibut (a deepwater fish), polar and Arctic cod, shrimp (kind of crustaceans), squid and octopus.

Variation: narwhals are one of the two species in the Monodontidae family, which may have evolved from the other: the beluga. They are very similar in physical appearance, but narwhals teeth structure consists just in two teeth, and one of them develops into a tusk that ranges from 2 to even 8 metres (the longest ever found).

Survival of the fittest: narwhals´upper skin has a greyish and motted pigmentation, that gives its name (narwhal means “corpse whale” in Old Norse) and that may be useful for camouflaging  in the deep waters of the Arctic.

Advantageous characteristics are passed on to offspring: narwhals able to avoid killer whales, because of their speed (they are faster, but killer whales attack them when they are unaware, knock them with a head impact and…) or their camouflage; or able to find a mate using echolocation; or capture more prey… in conclusion, being well-adapted, will have more possibilities of transmitting their genes to the next generation, and so these characteristics remain.

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