The male narwhal's extraordinary tusk results from the upper left incisor tooth growing out in a counter-clockwise direction. Females do not have a tusk. Like the antlers of deer, the tusk's sheer size might serve to signal the strength and prowess of its owner when competing with other males, for example for access to females. In old narwhals the tusk can be as long as 10 feet (3 metres), which is extraordinary given that the body length is only 15 feet (5 metres).

This photograph forms part of an album taken by the gunner of the 'Erik'. The album includes a further fifty-one photographs and the ship's log.

The 'Erik' was a Dundee whaling boat at the time when the photograph was taken. It sailed from Scotland to the whaling grounds at Baffin Bay in Canada. The Narwhal was known as the 'Unicorn' to the whalers and as Monodon monoceros to the scientist.

©SCRAN/National Library Scotland
Narwhal on the ice, 1876