Unicorns don't exist — or perhaps they do. They are not, however, horses with a horn on their forehead, but rather cetaceans with a long tooth that protrudes from the upper lip (in males), forming a long spiralling "sword".

What is a narwhal

We are talking about narwhals (Monodon monoceros), among the most iconic and mysterious creatures of the Arctic, which have fascinated explorers and scientists for hundreds of years and have likely given rise to legends about unicorns. Despite advances in science, these animals are still poorly understood, partly because of the remote and inhospitable places they inhabit — and it is precisely for this reason that many inaccurate beliefs about them persist.

"A lot of people don't even believe they're still alive," said Martin Nweeia of Harvard University. According to one of the most widespread myths about these marine mammals, narwhals skewer their usual prey — such as fish and squid — on their protruding tusks.

The narwhal's teeth and tusk

This is not the case, first of all for practical reasons. Narwhal teeth can grow up to three metres long, yet the prey they feed on is relatively small; impaling these animals would be genuinely difficult, and even if a narwhal managed it, it would have no other appendages long enough to retrieve the fish from its tusk.

Narwhals belong to the so-called "toothed whales", or odontocetes; however, contrary to what one might think, they do not chew their food. They have no teeth in their mouths — the only tooth they possess is the distinctive tusk.

Numerous theories have been put forward to explain the function of the narwhal's tusk: a weapon of defence or attack, an icebreaker, a courtship tool, a breathing organ.

According to the study Sensory ability in the narwhal tooth organ system, published in The Anatomical Record in 2014, the narwhal's tooth — densely innervated and rich in nerve endings — may help cetaceans sense water temperatures and changes in salinity, and perhaps locate their mates and prey.

Narwhals are today threatened by climate change and the growing human impact in the Arctic. In particular, noise pollution could disrupt the communication and orientation of these shy cetaceans.