The narwhals is a rarely seen Arctic whale. It is known for the very long tooth that males have. This long, single tooth or tusk projects from its upper jaw and can grow to be two to three meters long. The whale uses this tusk to pick holes in sea ice and to determine sea ice's thickness. Narwhals have a cylindrical body and a round head, with a small mouth on their blunt snout. This compact body shape, plus a thick layer of blubber retains heat in the icy Arctic waters in which they live.
The darker color on Narwhal's tops means that polar bears have to struggle to spot them against the dark waters of the Arctic. Since they are white underneath, killer whales find it difficult to see them against the brightness of the sky above. These protective markings that blend into the play of light and shadow in the sunlit upper Arctic and North Atlantic waters are important adaptations that the narwhals have. Another adaptation is that they feed mainly in winter when other whales migrate southwards. Thus, they manage to avoid competition for the available food.