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It's the age-old question: Why do narwhals have a unicorn horn?

Well, never fear, some scientists from Arizona, in the USA, might have the answer.

According to some brand new research, when it comes to narwhal tusks, size matters! That's because they use them for duelling!

Narwhals are a type of whale. They, like walruses and elephants, grow tusks which are actually modified teeth.

The tusks grow out of the narwhal's head in a spiral pattern and can be as long as eight foot, giving the creatures a unicorn-like appearance.

Generally, this trait is seen in males. Although, there are a few females who have tusks.

According to the research team at Arizona State University, the size of a narwhal's tusk is more important than the actual size of the narwhal when it comes to duelling.

That's because the information the tusk communicates is simple: "I'm bigger than you."

Those with bigger tusks gain an advantage in finding a mate because they are seen as more attractive and they are more likely to win in tusking contests against other males who are looking for a partner.