Scientist Plumbs Purpose of Narwhal's Horn

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A Harvard dental researcher says he's figured out the purpose of the giant, unicorn-like tusk seen on narwhal whales: It acts like an antenna that allows the narwhal to sense food and sea conditions. The dentist says the tusks are a giant tooth that grows inside out, with hard tissue inside and sensitive nerves on the outside.


We'll hear next about Arctic waters and a creature sometimes called the unicorn of the sea. It's the narwhal, a whale with a long, straight tusk, which was sometimes sold as a unicorn horn to gullible customers centuries ago. Kings and queens paid fortunes to have those tusks made into thrones and royal scepters. Until recently, nobody knew what the narwhal did with its tusk, but now a dentist who teaches at Harvard says he's figured it out, as NPR's John Nielsen reports.

JOHN NIELSEN reporting:

Martin Nweeia was sitting on an ice floe in the middle of the night when the narwhals finally showed themselves. First, a nine-foot-long tusk broke the surface of the Arctic Ocean, then a dozen more. He sat down on a plastic bucket and watched them dance across the water.

Dr. MARTIN NWEEIA (Harvard School of Dental Medicine): It was as if you had gone to some grand party where you were invisible. I felt like I shouldn't even talk or say anything or move just because I felt that if they somehow knew I had broken their trust that my opportunity would be gone.

NIELSEN: Nweeia is a practicing dentist in Sharon, Connecticut, and a lecturer at the Harvard School of Dental Medicine. He's also a leader of the Narwhal Tooth Expedition which for the last five years has been studying what he calls the King Kong of the tooth world.

Dr. NWEEIA: First of all, it's the only straight tusk that's known. It's also known to be one of the only spiral tooths.

NIELSEN: It's also really big. In a male Narwhal, the left tooth corkscrews out through the upper lip, regularly reaching a length of nine feet or more. And that's not the weirdest thing. According to Nweeia, the weirdest thing is that while every other tooth in the world consists of a pulpy core surrounded by a hard exterior...

Dr. NWEEIA: Narwhal is exactly opposite. No big surprise. It's been opposite in every other way. But to find a tooth that is soft on the outside and has its most dense part around the pulp was completely odd.

NIELSEN: What could the purpose of a tusk like this, Nweeia wanted to know? And so he wrangled a grant and set off for the Canadian Arctic leading a team of scientists and Inuit elders. At the time, some experts thought the narwhal used its tusk to poke holes through thin ice while others thought it used it as a weapon. Nweeia didn't think those theories worked for a tusk that had its soft parts on the outside. That hunch deepened when tests began to show that the pulp surrounding this tusk was extremely sensitive to water pressure, temperature and salinity.

Dr. NWEEIA: You can think of it as a weather station. It has those abilities to detect changes in both its water environment and its air environment. It has--you know, even when it pushes that tusk above the water, it has the capability to understand barometric pressure and temperature, even of the air.

NIELSEN: Nweeia says it's possible that further study of narwhal tusks could lead to advances in the field of human dentistry, but that's not why he spent five years chasing narwhals all over the Arctic.

Dr. NWEEIA: I just did this out of pure passionate interest. I kind of defy that old principle that Albert Einstein said that it's amazing that curiosity survives a formal education.

NIELSEN: Nweeia presents his findings today at a conference in San Diego. John Nielsen, NPR News, Washington.

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