Narwhals are sometimes called the unicorns of the sea, thanks to the long spiral “horn” that pokes out of the heads of the males. But it isn’t a horn at all. It’s actually one of the narwhal’s two teeth, grown so long and so straight that it comes out through the upper lip in a perfect twisted spiral up to 10 feet long.
For centuries, no one quite knew what the tusk was for. Defense? Mating display? Whacking ice? Then in 2014, a research team finally got a close look. The tusk contains roughly 10 million tiny nerve endings, all wired up to the narwhal’s brain. It’s sensitive.
The tusk works like a giant sensor probe, picking up tiny changes in water temperature, salt content, and pressure. Scientists think narwhals use it to navigate, find food, and judge water conditions as they cruise through the Arctic. It’s the only known tooth in nature that doubles as a sensing organ.
