All narwhals have two teeth in their upper jaw and a tusk. After the first year of a male narwhal's life, its left tooth grows outward, spirally. There are some narwhals that are double-tusked, but they are not as common. This long, single or double tooth projects from its upper jaw and can grow to be 8.75 feet (2.7 meters) long. Tusks are usually twisted in a counterclockwise direction and are hollow inside. The tusk's function is uncertain, perhaps used as a formidable jousting weapon in courtship and dominance rivalry, in getting food, and/or for channeling and amplifying sonar pulses (which they emit). The tusk is not used in hunting. Long ago, narwhal sightings probably reinforced (or started) the unicorn legends. In fact, when people found the horn of a dead narwhal washed up on shore, they thought that they had found the horn of a unicorn.