The narwhal is a medium-sized toothed whale that lives year-round in the Arctic waters around Greenland, Canada, and Russia. The males of this species are distinguished by a long, straight, helical tusk. It is in fact a canine tooth that projects from the left side of the upper jaw, through the lip and forms a left-handed helical spiral. The tusk grows throughout life and can reach a length of about 1.5 to 3.1 m (4.9 to 10.2 ft). It is hollow ...
and weighs around 10 kg (22 lb). About one in 500 males has two tusks, occurring when the right canine also grows out through the lip. Only about 15 percent of females grow a tusk, which typically is smaller than a male tusk, with a less noticeable spiral. Scientists have long speculated on the biological function of the tusk. Proposed functions include the use of the tusk as a weapon, for opening breathing holes in sea ice, in feeding, as an acoustic organ, and as a secondary sex character. The tusk cannot serve a critical function for the animal's survival, as females (which generally do not have tusks) typically live longer than males. Therefore, the general scientific consensus is that the narwhal tusk is a sexual trait, much like the antlers of a stag, the mane of a lion, or the feathers of a peacock.
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