Which whale has a single long tusk that can exceed 3 metres?

The narwhal is the whale whose single tusk can exceed 3 metres.

A narwhal’s tusk is actually an elongated upper-left canine tooth that grows through the animal’s upper lip. It is most common in males, although some females also develop one. Rarely, a narwhal grows two tusks.

Narwhals live in Arctic waters around Canada, Greenland and Russia. They migrate seasonally between coastal areas and deeper offshore habitats, following sea-ice conditions and prey such as Arctic cod and squid.

The tusk has millions of nerve endings and can detect changes in the surrounding water. It is not a horn, despite the familiar nickname “unicorn of the sea.” Narwhals are toothed whales and are closely related to belugas.