AILSA CHANG, HOST:
The cold waters of the Arctic are home to an unusual whale that you might have heard of, the narwhal. Narwhals have a long, sharp tusk that juts out of their heads. As NPR's Nell Greenfieldboyce reports, scientists recently used drones to spy on narwhals and were intrigued by how these whales seemed to use their tusks.
NELL GREENFIELDBOYCE, BYLINE: The tusk that sticks out of a narwhal's head can be up to 10 feet long. Greg O'Corry-Crowe is a zoologist with Florida Atlantic University. He's gotten to see this tusk up close while working to tag narwhals with satellite trackers.
GREG O'CORRY-CROWE: And it is quite an overwhelming experience to stand there in the water and help hold a live narwhal and sort of feel the tusk.
GREENFIELDBOYCE: He says the tusk is beautiful.
O'CORRY-CROWE: It almost looks like it has been fashioned and carved. It has a lovely spiral, scrolled pattern to it, so it's mesmerizing really in some ways.
GREENFIELDBOYCE: Hundreds of years ago, seafarers brought these home and passed them off as unicorn horns.
O'CORRY-CROWE: It almost seems like it was the strongest proof that unicorns really did exist.
GREENFIELDBOYCE: Why the narwhal tusk exists has long been of interest to scientists. The tusks are found almost exclusively on male narwhals. There's now a general consensus that the tusks play a role in competitive mating. A long tusk tells females that a male is large, fertile and successful - the bigger, the better.
O'CORRY-CROWE: So I think in many ways, we've sort of converged on that as the primary use, but it looks now like it has other uses.
GREENFIELDBOYCE: He thinks that because he and some colleagues recently spied on groups of narwhals. They used small drones that could hover above the water and take video. They did this research in the summer. The water was clear enough to see down 15 feet or so. The narwhals seemed to be relaxed, just gently socializing.
O'CORRY-CROWE: Females were nursing calves. Males were hanging out in these sort of bachelor herds.
GREENFIELDBOYCE: Some of the narwhals with tusks seemed to use them in a playful way, to explore or manipulate fish.
O'CORRY-CROWE: You know, mess with it with their tusk, flip it a few times, flip it again - you know, things like this. And then, you know, they would turn to each other as if saying, you know, you have a go or, you know, this is what you do.
GREENFIELDBOYCE: In the journal Frontiers In Marine Science, the researchers say narwhals could use their tusks to stun and possibly kill prey. They saw a narwhal repeatedly hitting a fish with its tusk. Cortney Watt is a scientist with Fisheries and Oceans Canada. She notes that females get food just fine without tusks, so she doesn't think this is why the males evolved to have them.
CORTNEY WATT: But I think maybe they've learned to use them to assist them with foraging.
GREENFIELDBOYCE: One narwhal expert who didn't work on this study is skeptical. Kristin Laidre is a marine biologist with the University of Washington.
KRISTIN LAIDRE: I think these are short-term videos that show a few narwhals at the surface, you know, moving their heads around in the vicinity of a fish. And whether it's play behavior or pursuit of that fish to consume it, nobody knows.
GREENFIELDBOYCE: She says narwhal behavior remains largely unknown. There's almost no underwater observations.
LAIDRE: There's so much we could learn if we could, you know, have images or video or something down there, seeing their behavior and being able to record it.
GREENFIELDBOYCE: But she says even if you could have an underwater drone, these skittish whales would no doubt be scared away. And for much of the year, narwhals are completely out of reach. They spend the long, dark Arctic winter far offshore, living beneath the sea ice, diving deep in frigid water. Nell Greenfieldboyce, NPR News.
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