In my recent blog, simply titled "Narwhals" I mentioned that science has so far not found any use for the narwhal tusk, and no one could figure out why its there. Well, this article from 2005 actually explains that we have actually found a possible purpose. I'm going to sum up the article, and leave a link at the bottom.
I hope that everyone here knows that a tusk is a tooth, but the narwhals have slightly odd ones. While elephants and warthogs have curved tusks, the narwhal is the only animal known to have a straight one, and their tusk actually spirals around, if you noticed in the pictures. The spiral could serve to provide more rigidity so it will not break, or to help it grow straight. It isn't certain. Anyway, while the tooth is straight, it can actually bend in any direction! Furthermore, it is actually very strong and is hard to break.
That is only one discovery, however. I read about a few more. One that I'm going to cover really quick is that the narwhal tusk is a tooth, but a tooth that is inside out. You know how your teeth are very sensitive to especially cold foods? Narwhal teeth sense this even more strongly, but probably for the purpose of sensing environmental changes around them. I would assume it doesn't actually hurt them, seeing as they are constantly exposed to it. They might be able to sense ice forming miles away. They have also been known to dive as deep as 3000 feet when avoiding danger or hunting for food. There is also another theory that narwhals might use their tusks to communicate with each other, generally with tapping. Obviously, it isn't their only form of communication, but it is possible to be a way. As far as the inside-out stuff goes, there aren't any other teeth in the world like it. That is super awesome.
Another thing I don't know if I mentioned, but I had the impression of was that only male narwhals had tusks. Actually, this is not true. Apparently, most males have one tusk, some have two, a few don't have any, and oddly enough there are females who do have one. So it sounds like it is all very awkward and who knows how that works. If I were a narwhal, I would feel gypped if I didn't get a tusk and some other guy got two, but oh well. All I can do is stand by and feel sorry for them. Then again, they have an excuse to tell the ones who do have tusks what to do and cling to them so they can be lazy.