A narwhal is a medium-sized whale that lives in the cold Arctic waters around Canada, Greenland, and Russia. What makes narwhals instantly recognizable is the long, spiraling tusk that grows from their upper jaw, sometimes reaching ten feet long. This tusk is actually an overgrown tooth, and it looks so much like the horn of a mythical unicorn that narwhals are sometimes called “unicorns of the sea.”

For centuries, people debated what narwhals used their tusks for. Scientists now believe the tusk works as a sensory organ, helping narwhals detect changes in their ocean environment, like water temperature and salt levels. Male narwhals sometimes cross tusks with each other in what appears to be a form of communication or play rather than fighting.

Narwhals are incredibly well-adapted to Arctic life. They can dive nearly a mile deep and hold their breath for twenty-five minutes while hunting fish and squid. They travel in groups called pods, often staying together for years. Because narwhals live in remote, icy waters, they remained mysterious to most of the world until quite recently. Today, scientists study them to understand how marine mammals survive in extreme cold and how climate change affects Arctic ecosystems.