Which marine mammal is famous for males having a long spiral tusk? The answer is the narwhal.
The narwhal (Monodon monoceros) is an Arctic toothed whale and the only living species in the genus Monodon. Its celebrated tusk is usually the left canine tooth, which grows through the upper lip and can become several metres long. It is hollow, spiralled and continues growing throughout the animal’s life.
Most males develop a tusk, while females usually do not, although females can rarely grow one. Some males also develop two tusks when the right canine erupts. Narwhals sometimes rub tusks together in a behaviour called “tusking,” probably connected with social status.
The tusk is often mistaken for a horn, but it is actually a tooth. Scientists have proposed roles in display, competition, sensing the environment and feeding, but no single function explains every observation. Narwhals live mainly in Arctic waters and make exceptionally deep dives beneath sea ice.