How do narwhal tusks grow?

Narwhals are sometimes called “the unicorns of the sea” because of their giant spiral tusks. It turns out that those tusks are actually a big tooth that grows right out of the narwhal’s mouth! One of our listeners wanted to know if narwhals were born with a hole in their head for the tusk, and if not, does it hurt the narwhal when the tusk comes through? We spoke with marine biologist Kristin Laidre to get the tooth – er, the truth. If you’ve got a whale of a question for Moment of Um, you can send it to us at BrainsOn.org/contact!