The Mystery of the Unicorn of the Sea Solved

Narwhals use their long tusk for echolocation to see the ocean around them. (Photo credit: Dr. Kristin Laidre, Polar Science Center, UW NOAA/OAR/OER)
For many centuries, the mystery of the narwhal’s tusk has persisted in scientific journals and traditional folklore alike. Now, new research has solved the mystery of the sea unicorn.

For many centuries, the mystery of the narwhal’s tusk has persisted in scientific journals and traditional folklore alike. Now, new research has solved the mystery of the sea unicorn.
 

In the depths of the Arctic Ocean around Greenland, Canada, and Russia lives the narwhal. A medium-sized toothed whale of the Monodontidae family, male narwhals have evolved to grow an extra long canine tooth that protrudes through the upper lip and out from the head like the horn of a unicorn.

Measuring up to 2.9 meters in length, there has never been decisive research on the use of their imposing tusk. Scientists have speculated that these tusks signaled to female narwhals the testicle size of a mate; that they are used as ice picks; or that that they act as defensive weapons in contests between males to win mates.


In 2014, a study published in The Anatomical Record gave humanity its first conclusive clue to what these tusks really are: a sensory organ.

The study, led by Dr. Martin Nweeia of Harvard School of Dental Medicine, found that the tooth had no hard, external enamel to protect it, making it sensitive to the tiniest stimuli. Sea water enters through the cementum channel of the tusk through a network of tubules to the center. The water then excites nerve endings and sends signals back to the brain, giving the whale a taste of the ocean around him. Although an important clue, the 2014 still left many questions unanswered in the great mystery of the narwhal’s tusk.

That all changed with a recent publication in the journal Pols One by Dr. Kristin Laidre and her team of researchers. They discovered that narwhals use their tusks to see the marine world around them.


A Flashlight for Seeing in the Polar Night

"These are the first data ever collected from narwhals in the winter pack ice using a vertical array," Dr. Laidre of the University of Washington told High North News. "We have discovered some incredible things about narwhal echolocation and their ability to use sound underwater to "see"."

Echolocation, or bio sonar, is used by a number of different marine mammals like dolphins and whales to help them navigate in dark and murky waters without straining their weak eyes. Instead of perceiving their environment and obstacles with their eyes like humans, narwhals use clicking sounds, listening to the sound wave echoes of nearby prey or rock formations to reconstruct their surroundings.

Living the extreme marine environment of Arctic Ocean, narwhals scan vertically as they dive to help find patches of open water amid sea ice cover and food in dimly lit waters. lets sunlight through to.


At a rate of up to 1,000 clicks per minute, the sounds cannot be heard by the human ear – but give narwhals the most directional sonar of any species on earth. Directional sonar means that instead of taking in a vast array of objects all at once, narwhal clicks hone in on singular, high resolution snapshots of their environment to piece together the larger picture.

"If you imagine they use sound like a flashlight," Dr. Laidre describes, "basically have a highly adjustable flashlight and can focus the light (or in their case sound) beam in a very narrow area. This information begins to help us piece together how these animals live and navigate in such an extreme environment."


But the journey to collect this incredible information wasn’t easy.


A Perfect Lineup for Sonar Data Collection

"There were many challenges with this project." Dr. Laidre said. "Many things had to 'line up' for us to be able to even have the right conditions to collect the data."

Dr. Laidre and her team of dedicated ecologists placed waterproof sound recorders, called hydrophones, at 11 ice sites in Baffin Bay, west of Greenland in 2013. The hydrophones were placed at a depth between 3 and 18 meters to collect data on the narwhal population’s clicking sound and response to the echoes. But to do this, the Arctic’s harsh environment needed to ‘line up.’

"We needed safe and stable (clear) weather to be able to fly 100 km offshore in a helicopter and land on the pack ice. We needed solid and safe pack ice conditions for landing and working near cracks/leads where narwhals occur. We needed conditions on the ice that allowed us to set up and record data, such as low winds and manageable temperatures. We also needed to have narwhals present in the vicinity of our recording equipment and ideally have the whales stay close for several hours. We also needed our equipment to function in extreme conditions including low temperatures and icing.  We had a lot of failures, meaning all of these things did not line up to make it possible to collect data. It took a lot of patience."

Patience, and some help from the local community of Niaqornat, a 58 person settlement in Greenland.

"We worked with the local community where we were based (Niaqornat, West Greenland which is located on the Nuussuaq peninsula north of Disko Island). They assisted us with the project several ways - of course by providing advice and input on the conditions and the whales, but also helping us with setting up fuel depots and housing. We gave talks in the school for the children and shared the results with the community."


Narwhals New Enemy: Noise Pollution

But with such sensitive sonar to ‘see’ the marine environment that surrounds them, narwhals may be disturbed by the noise pollution from increased tourism cruises and shipping use in the region.  Dr. Laidre’s work creates a foundation for better understanding just how much noise pollution may disturb the unicorns of the sea.

"We know very little about narwhals in general. They are a difficult species to study and there are large gaps in our basic knowledge. This information provides a baseline for how narwhals use sound and begins to allow us to understand how increasing noise in the Arctic may impact the species."


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