A video taken by a drone in Canada's remote Arctic Ocean has captured narwhals using their massive tusks, which are actually enlarged, protruding teeth, to hunt fish by whacking them first. According to scientists who studied the video, this seems to temporarily subdue the fish before the narwhal devours it.
There are plenty of theories around the function and purpose of a narwhal's mighty spiralling tusk, which can grow more than nine feet long. Some have speculated it could be related to mating, or used as a sensory organ because the tusk itself has a lot of nerves. One paper found that testes mass in male narwhals correlated with tusk size, leading them to believe that the tusk is a way for males to attract females: males, for the most part, are the ones who develop the tusks. This is the first time that evidence of its use has been recorded.
"This is not to say that now we've figured out what the tusk is for," said Brandon Laforest, the senior specialist on Arctic species and ecosystems for WWF-Canada, the environmental nonprofit that worked on the drone shoot. But it's a jumping-off point that will help scientists better understand narwhal behaviour, he said.
Other animals, like owls, sharks and electric eels, use a stun-first-then-eat practice, but bopping fish is not the only way that these unicorns of the sea hunt. According to Laforest, horned females only make up five per cent of tusked narwhals, but those without horns also have to get their chow. Since narwhals spend their time along the Baffin Bay Continental Shelf in the winter, "it's impossible to know what they're doing down there," he said.
"The majority of the food comes during winter season, when (the narwhals) are in Baffin Bay and they hunt for halibut in deep, deep waters," Laforest said. The video, shot while narwhals were summering in Tremblay Sound, Nunavut, "confirms that they also feed throughout their migration."
Laforest said this could also help scientists understand habitat use, specifically where narwhals feed, mate, birth and raise their calves. With that information, certain areas, like ones that are often used for shipping and cruise ship routes, can be set aside for protection to minimize disturbances to the animals when they're feeding, giving birth and raising their young.
"By no means has the complete function of the tusk been figured out," said Laforest. "But, it's definitely a novel use and will be contributing to further research." Subscribe to Science Solved It, Motherboard's new show about the greatest mysteries that were solved by science.