SCIENCE LAB SPECIALS : FISH TRICKS

FOR an animal with an ivory appendage half the length of its body protruding from to top of its head, a narwal moves in the water with surprising grace.

'' It's almost mesmerizing,'' said Greg O'Corry-Crowe, a research professor at Florida Atlantic University. '' The precision with which they wielded their tusks, it wasn't like a broadsword. It was like a surgical instrument or the bow of a violin.''

In research published in the journal Frontiers in Marine Science, Dr. O' Corru Crowe and colleagues make the case that narwhals weren't only showing off with their tusks, the appendages have a variety of uses that help the animals survive in the ocean.

The narwhal's tusk was an inspiration for unicorn myths. It's known that only males have them, with rare exception, and that a big tusk is something female narwhals look for in a mate. But the shy and elusive animals have been difficult to study.

With the help of local Inuit communities, the team of researchers identified spot in the Canadian High Arctic to set up camp and fly drones.

As Dr. O'Corry - Crowe and team studies their video recordings, they identified previously unobserved tusk behaviours. And of those behaviours looked an awful lot like playing.

Narwhals sometimes chased arctic char but did not, strangely, try to catch and eat it. The whales even slowed down when necessary to keep the fish just off the tip of their tusks.

When they did interact with the fish in these encounters, they used gentle taps or nudges - a stark difference from more aggressive uses of their tusks when they were seen hunting fish.

And in fact, the arctic char also didn't seem to always be trying to escape the pursuing narwhals.

'' They ate not actually foraging on the fish, and we were hesitant to use the word  'play', but that is really what it looked like,'' said Cortney Watt, with Fisheries and Oceans Canada, and an author of the study.

She said it was also possible older narwhals used such behaviour to teach younger ones how to pursue prey.

The World Students Society thanks Kaleigh Rogers.