The Narwhal: a Real Sea Unicorn

The narwhal is a whale that lives in the freezing seas around northern Canada, Greenland and Svalbard, swimming between the cracks in the sea ice. A big male is about five metres long — longer than a car — and out of the front of his head grows a long, pale, spiralled point that looks exactly like the horn of a unicorn.

Almost every male narwhal grows one. Most females never grow a tusk you can see — and here is a chance to use this hall's own rule. How many females do? You will often read 'about one in seven', but scientists who counted a group of narwhals properly and published their work found far fewer than that. Nobody has settled it. The narwhal's scientific name is Monodon monoceros, which comes from old Greek words meaning 'one tooth, one horn'.

The tusk always twists the same way round, like a screw, in every single narwhal — and scientists are still arguing about why. Inside it there are millions of tiny nerve endings, which is very unusual for a tooth. Many scientists now think the narwhal can feel the water through its tusk: how salty it is, how warm it is, perhaps what is swimming nearby.