These “unicorns of the sea” seem to be everywhere: on T-shirts, mugs, and more. But in their native Arctic waters, they’re hard to spot.

The narwhal with its unique, spiraling tusk has inspired legends in Inuit society and fascinated people across cultures for centuries. On Aug. 3, a new exhibition at the Smithsonian’s National Museum ...

Narwhal, the 10-week-old puppy with a tail growing between his eyes, at Mac’s Mission animal rescue in Cape Girardeau, Mo., on Wednesday. Credit ...