The Unicorn of the Sea – December 16, 2020
As the holidays approach, we’re focusing on the cold places of the planet – while harsh, these places are home to many incredible and resilient species. One that stands out for its uniqueness is the “unicorn of the sea” – the narwhal. This whale species spends its life in the Arctic waters of Canada, Greenland, Norway and Russia and feeds on fish, squid and shrimp. They can dive about a mile deep in the ocean!
The most striking feature of the narwhal is its tusk – which isn’t a tusk at all. In fact, it’s an overgrown tooth that can grow up to 9 feet (2.7 m) long and is incredibly sensitive on the outside – with up to 10 million nerve endings. Speaking to the sensitivity of this tooth, as one example, scientists found significant changes in heart rate when narwhal tusks were exposed to solutions of salt versus freshwater. Read more about the 2014 study here:
The tooth is actually pretty flexible – it can bend about a foot in any direction – and it is much softer on the outside and gets increasingly harder and denser on the inside (see image of the tooth anatomy below). Given these characteristics, you can think of it as an “inside-out” tooth (our human teeth are hard on the outside and softer/pulpier on the inside). Male narwhals typically have a prominent tooth that grows over time, while females have them infrequently. So, if you spot two narwhals “tusking,” or, crossing tusks like they are in a fencing competition, more than likely they are males. Despite years of speculation, we still don’t have a clear understanding about the tusk’s function, because narwhals spend most of their lives hidden underneath the Arctic sea ice. But the 2014 study as mentioned above provides many new insights into the multi-functionality of this tooth – with the biggest conclusion focused on the incredible sensitivity.
While hunting, narwhals don’t use their tusks to spear their prey, as fish are simply too small. If a narwhal somehow managed it, it would not have any other appendages long enough to retrieve the prey from its tusk anyhow! Scientists have recently seen narwhals using their tusks for feeding by giving quick and firm “tusk taps” to momentarily stun their prey before quickly sucking them up: https://www.youtube.com/watch?v=OoTjLIN67Bw
photo: U. Horodyskyj