The enigma of the one-tooth unicorn

Narwhals "tusking" - US DOJ photo

Narwhals “tusking” – US DOJ photo

For a creature that figures so well into European mythology, the Narwhal carries with it surprisingly few myths of its own. As its Linnaean taxonomic binomial infers, Monodon Monoceros (one tooth, one horn) the narwhal was described by Europeans as a “sea unicorn.”

In the late 16th century English explorer Martin Frobisher returned from northern Canada with a tusk for Queen Elizabeth. She was so taken by the gift she had it placed among the crown jewels. This in turn stimulated a lively trade in the tusks which were harvested by the Vikings and sold as “real” unicorn horns to naïve royalty in Europe. I say “royalty” because these fetched prices equivalent to “the cost of a castle” at the time.

Excavating into the indigenous tales yields precious few stories. The one Inuit account tells of a blind boy who was maltreated by his cruel mother. When the Loon comes to heal the boy by washing his eyes in seawater the mother becomes more cautious around him. But not cautious enough, because as they hunt together the boy spears an unusually large Narwhal. With the rope tied around the mother’s waist she is pulled into the sea where her hair entangles with the spear to become a narwhal tusk.

In the annuls of western speculative biology the tusk had “naturally” been considered an object of comparative advantage. How could something so long and “pointy” not be used as a weapon? How could something so extended on some individuals (up to 3m!) and not on others not be an expression of sexual dominance? It’s typical sexually dimorphic appearance might substantiate this – except that some females have tusks as well. And that the males that sport the longest tusks don’t appear to skewer each other with them – in fact they are more often seen rubbing each other’s tusks nicely.

The tusk is actually and armature for a spiral wrapping of nerves – so it is a sense organ. Perhaps like an exposed olfactory system. Some fairly blunt research has confirmed that exposing the tusk to fresh or salt water induces metabolic responses in the creature. But I suspect that in the testing setting the metabolic stress response of the captive subjects was orders of magnitude higher than what such a proud sense organ might induce in their natural habitat. If indeed the tusk does sense chemistry, what subtle chemical signals might it reveal?

More nuanced research by Jens Koblets et al. has recently been published about narwhal echolocation signals. Using arrays of hydrophones, the team found that the narwhal’s echolocation clicks are more focused than any other marine mammal yet measured – forming and casting asymmetrical beams 5° wide – and measurable at 100m! The asymmetry is important here because like the asymmetry of the acute hearing organs of owls, it may tease out fine distinctions in the returning signals that they hear – allowing them a detailed acoustical construction of their often dark Arctic ocean environment.

Of course we will never truly know how the narwhals perceive and interact with their surroundings. We’ve made some bad guesses. Even the myths don’t venture far into what it might be.

I’m humbled by this mystery, and thankful that I get to wonder about it.

Have a Happy Thanksgiving!