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9:59:0 
2025-03-05 
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With a fabled ability to purify tainted water or heal ailments, the narwhal's spiraling tusk was highly coveted during the Middle Ages when it was mistaken for a unicorn's horn.
As narwhals (Mondon monoceros) are almost as elusive as the fantasy they helped fuel, researchers have had a tough time determining what the marine mammal's oddly elongated tooth is actually for.
Drone footage of a pod in their Arctic habitat now provides some unexpected answers, with the animals using their tusks to manipulate objects, forage, explore, and even play.
"I have been studying narwhal for over a decade and have always marveled at their tusks," says University of Manitoba ecologist Cortney Watt. "To observe them using their tusks for foraging and play is remarkable."
The tusk, which can grow up to 3 meters (9 feet) long, is the only tooth possessed by these toothed whales. Like the rings on a tree, its growth layers record an individual’s life history.
Yet most female narwhals lack tusks, revealing the spear-like tooth is – at least in part – involved in sexual selection. Females prefer males with longer tusks, placing evolutionary pressure on populations to grow even longer tusks similar to how male peacocks are encouraged to grow such elaborately fancy tails.
That doesn't mean the tusk is purely decorative. A previous study discovered the tusk is also crammed with nerves, hinting at more complex roles.
The new footage and analysis confirm the narwhal's mysterious tooth has a sensitive side.
"Narwhals are known for their 'tusking' behavior, where two or more of them simultaneously raise their tusks almost vertically out of the water, crossing them in what may be a ritualistic behavior to assess a potential opponent's qualities or to display those qualities to potential mates," explains Florida Atlantic University ecologist Greg O'Corry-Crowe.
"But now we know that narwhal tusks have other uses, some quite unexpected, including foraging, exploration, and play."
O'Corry-Crowe and colleagues filmed a pod of narwhals using their tusks to manipulate the behavior of fish with remarkable precision while tracking their prey's movements. This included stunning or possibly killing them.
"The whale and fish movements were so closely mirrored, it was unclear at times which animal was the primary actor and who was the responder," the team writes in their report.
In another sequence, a younger narwhal tried to copy the technique of an older individual who was hot on the heels of a fish, the senior narwhal's tusk within centimeters of the prey. The younger hunter's tusk came barely within a meter of its target.
Neither mammal actually tried to eat the prey, suggesting this was practice or even a form of entertainment. If so, it may be the first ever evidence of play in the creaking and chirping narwhals, as well as a possible example of social learning, the researchers suggest.
Sadly, the shielding sea ice these sea unicorns rely on to avoid their predators, like orcas, is now rapidly melting thanks to human-caused global warming. The Arctic is warming four times as fast as the rest of the world, and narwhals are considered the region's most vulnerable marine mammals.
"Drones provide a unique, real-time view of their behavior, helping scientists gather crucial data on how narwhals are responding to shifts in ice patterns, prey availability, and other environmental changes," says O'Corry-Crowe.
"Such studies are key to understanding the impact of global warming on these elusive animals."
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