Narwhals are a species of whale. They live in Arctic waters. Because the male has a long, spiraling single tusk, narwhals are known as the unicorns of the sea. Researchers wanted to know more about these elusive creatures. So they attached recording devices to their backs. The devices were stuck on with suction cups and string. The string was made to degrade quickly in the water. Once it broke apart, the devices floated to the surface, where scientists could retrieve them. When the scientists listened to the recordings, they heard clicks, whistles, buzzing, and trumpet sounds. The whales made the sounds at different depths and while doing different things.