The narwhal, Monodon monoceros, is a small whale that reaches a maximum length of 5 m. It has a more limited distribution than the beluga, being restricted to the eastern Arctic in the vicinity of Baffin, Devon, and Ellesmere Islands. Adult males have a long, spirally twisted tusk, which projects through their upper lip and is hollow for most of its length. Although these tusks may reach a length of 3 m, their function was long uncertain. However, as they occur only in males, they are probably used to establish dominance in the social hierarchy and as a visual display of strength. Roughly every one in three tusks are broken and most adult males bear scars on their heads from fighting.
Narwhals are gregarious, sometimes congregating in herds of more than 1000 animals which are so noisy they can be heard several kilometres away. These herds are usually segregated by age and sex. The narwhal often dives as deep as 400 m as it forages on squid, shrimp, polar cod, and other fish. Young are born in June and July and in the autumn large groups form, which overwinter in polynyas. Recent estimates suggest that there are approximately 30,000 narwhals in the wild.
Canadian Inuit have long valued the narwhal and hunted it for its tusk and thick skin, which is traditionally eaten raw as a delicacy. Commercial whalers targeted this species in the 17th century and sold the tusks to China and Japan, where they were used in traditional medicine because of their association with the fabled unicorn.