The tusk of a narwhal is actually its extended long tooth. It has not been determined what it is used for, but there are many valid theories, all with a certain degree of evidence to support them.

Answer #1

The suggestion that the narwhal horn is used for aggression, fighting, and sea ice breaking isn't the conclusion that Charles Robert Darwin [February 12, 1809-April 19, 1892] came to. Subsequent research is influenced by Darwin's writings. His conclusion and that of later researchers who accept Darwin's investigations tend towards the social uses of the narwhal's horn. So the horn is used to indicate social rank, remind other narwhals of the individual's dominance, and train younger males in skills as a sexual predator.

Answer #2

In this regard, Darwin speculated that the horn might serve a similar function to that of a stag's antlers. As always, it should be remembered that Darwin's theory was just that - theory, and not fact, as there was insufficient evidence to prove the point.

Answer #3

It is unknown what a narwhal uses its tusk for. It is believed to be used in courtship and as a weapon against other males. There is even speculation that it may be used to enhance the narwhal's sonar functions.

Answer #4

Another strong possibility is that the tusk is used for sensing things in the water, such as fish, or it is used to sense when it is time to migrate. The tusk of a Narwhal is said to be sort of like an exposed nerve. When scientists used an electron microscope on a narwhal's tusk, they found 10 million nerve endings extending from the core of the tusk toward the outer surface. They concluded that these nerve endings could detect subtle alterations in temperature, pressure, particle gradients and a variety of other sensory changes.