STEVENS POINT, Wis. (AP) — He's a dentist with an engineering degree, an insatiable curiosity and a sense of adventure, all of which has compelled him to study one of the strangest animals in the world.

He's Dr. Fred Eichmiller, 62, the bearded, low-key, quick-to-chuckle vice president and chief science officer of the Stevens Point insurance company Delta Dental of Wisconsin. But in his free time, he's been pursuing a quest to learn more about the so-called "unicorn of the sea," the narwhal.

The narwhal is a northern sea-going mammal, the males of which sport long, swirling tusks that jut out of their faces. Eichmiller's passion for the narwhal has led him on expeditions above the Arctic Circle, and his work is now part of a groundbreaking exhibit at the Smithsonian National Museum of Natural History in Washington D.C. "Narwhal: Revealing an Arctic Legend" will be on display in the institution into 2019.

Eichmiller's narwhal journey, he said, centers on one basic question: "Why in the world would a whale grow a 9-foot tooth out of its forehead?"

USA Today Network-Wisconsin reports that his quest started about a dozen years ago, before he moved to Stevens Point to work for Delta Dental. At the time, he was a clinical research science director and managing director for the American Dental Association Foundation's research center in Gaithersburg, Maryland.

One day, the center got a phone call from Dr. Martin Nweeia, a dentist based in Connecticut. Nweeia is also a member of the National Geographic Explorers Club, and he was in the midst of studying the evolutionary purpose of the narwhal's tusk. The tusk is not a horn; it is a tooth with nerves running its entire length. However, it does not have a hard enamel surface, like a human tooth.

"It's almost all dentin, a coating which is softer," Eichmiller said.

Nweeia called the research center to enlist help in studying the makeup of the narwhal tusk. Eichmiller quickly agreed, and just as quickly got absorbed in what Nweeia was trying to accomplish. Up until Nweeia started scrutinizing the tooth, the marine biologists of the world theorized that the tusk's primary purpose was to attract a mate. The bigger the tooth, that thinking goes, the more likely a guy narwhal would have success in finding that special lady narwhal.

But the presence of the nerves in the tooth puzzled Nweeia and Eichmiller. If the tooth was for show, or to battle other male narwhals for female attention, why were the nerves there?

The dentists' theory was that the tooth could be used as a sensory organ. But the problem was how to test that theory. How can one expose a narwhal's tooth to different stimuli, such as amount of salt in the water or temperature?

The engineering background came in handy. Eichmiller designed a kind of bladder that could be placed over a narwhal's tusk, and highly salty water could be pumped into it. The narwhal's reaction could be measured by tracking its heart rate and other biometric information.

Eichmiller and Nweeia went on a few expeditions to northern Canada, where scientists were capturing narwhals and attaching tracking equipment on the animals. That's how Eichmiller found himself with a team of researchers in waist-deep water, holding the tusk of a narwhal.

"It's pretty amazing," Eichmiller said.

The two dentists found that narwhals indeed react to amount of salt in water. They theorize that the ability can help the narwhal survive in a variety of ways. It can help the animal find food. Narwhals eat cod, halibut and other kinds of fish, some of which can be found along coastal waters where freshwater drains into the sea.

Maybe the sensitive tusk helps the whale find its way to cracks in Arctic ice. The mammal spends a lot of its time under the ice, but it also has to find its way to the surface to breathe.

Nweeia and Eichmiller carefully wrote up their findings in a scientific paper. "We were dentists in a world of marine biologists," Eichmiller said. "We knew once we were published, we would be scrutinized very closely."

The paper led to the Smithsonian exhibit, and soon a book chronicling their work will be published through National Geographic.

Meanwhile, Eichmiller and Nweeia will continue to learn more about the strange narwhal tooth.

"You get to be involved in something that very few people have a chance to study," Eichmiller said. "And it's intriguing."

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Information from: Wausau Daily Herald Media, http://www.wausaudailyherald.com