Narwhals (Monodon monoceros) are a type of toothed whale, best known for their long unicorn-like tusk. The tusk is normally found on male narwhals and is actually a tooth. Narwhals usually live in groups of two to ten and form slow-moving herds that dive to feed on crustaceans, fish and squid. They live in deep Arctic waters during the winter and migrate to more coastal, ice-free Arctic areas in the summer.