Classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Suborder: Odontoceti
Family: Monodontidae
Species: Monodon monoceros

Overview

Narwhals are medium-sized with a length (minus the tusk) of around 4 to 5.5m, and a weight of around 800 to 1,600kg. Groups of narwhals usually only contain females and young, although mixed-sex groups can aggregate at any time of the year. In the summer, however, groups join together to create larger groups of over 1000 individuals.

Behaviour

Every year narwhals undertake seasonal migrations from coastal bays in the summer into the frozen open ocean during the winter. Here they take advantage of fissures in the ice in order to take a breath. Groups of narwhals can often be seen moving along these cracks in the ice in a long line.

Narwhals feed on cod and similar fish in the summer and flatfish and other bottom-dwelling prey in the winter. During the winter they can dive up to a maximum depth of 1,500 metres while hunting for prey.

With a lifespan that can last up to 50 years in the wild the main threat to narwhals, other than that of human action, comes from suffocation or starvation when the sea freezes over.

That Curious Tusk

Throughout the ages explorers turned up with huge spiral objects that most believed to be the horn of a unicorn. How wrong they were. Eventually, it was discovered to be the upper left incisor of male narwhals!

The tooth projects from the left side of the upper jaw out through a hole in the lip. Growing throughout its life, the tusk can range between 1.5 and 3 metres in length. Being hollow it only weighs around 10 kg, quite light for such a large object. Incredibly, about one in 500 males actually grows two tusks!

Sir David Attenborough muses in David Attenborough's Natural Curiosities that the spiralled nature, a left-handed helix, may help to keep the tusk straight although there are several other theories. It is widely accepted that the tusk's role is as a secondary sexual characteristic, similar to the lion's mane or peacock's tail feathers. The tusk may help male narwhals to determine its social rank in a group, via passive jousting or posturing. There are also suggestions that he tusk may in fact be a sensory organ.

Quick Facts

• The tusk used to be mistaken for that of a unicorn's horn.
• The tusk is the narwhal's upper left canine.
  
• Feeds on prey on the bottom of the ocean at depths of up to 1500m under the ice.
  
• The scientific name, Monodon monoceros comes from the Greek "one-toothed unicorn".
  
• Weight-for-weight, narwhal tusk used to be more valuable than gold.