A narwhal's tusk makes it weird among whales. It's actually a tooth that can reach ten feet in length, and scientists have numerous theories about its powers and purpose.

Male narwhals can weigh nearly two tons, with bodies up to 16 feet long.

But it's their tusks that make them weird among whales. The tusk is actually a single gigantic tooth that can reach 10 feet in length.

But why swing such a big sword? Scientists aren't exactly sure.

Narwhals are an animal of misinformation and mystery, dating back to the Middle Ages when their tusks were fobbed off to royalty as unicorn horns.

Is it used to impale their prey? No!

Narwhals can dive more than a half mile down to the ocean floor to feast on cod, squid and cuttlefish. No stabbing or goring required.

Is it used to poke around on that dark ocean floor? Possible, but improbable. Narwhals, like their dolphin cousins, use sonar to guide them through the depths. The tusk is jam-packed with nerve endings.

Some scientists argue it acts as some kind of sensor, that would be one insightful incisor.

But it's the males who predominantly sport the tusks.

If the tusks had a survival advantage, the females would also be long in the tooth.

Some scientists believe this means the tusk serves the same function as a deer's antlers or a teenager's hotrod: a way to show who's the fittest male around.

Males occasionally cross swords. That's tickling the ivories. But whether it's a joust or a jaw session is anybody's guess.

And the narwhals aren't telling.