Heartbeat of a Unicorn: The Latest in Narwhal Research

December 11, 2017

We all know that narwhals are quite clearly the coolest animals in the ocean. But did you know what their heartbeat sounds like? And why this sound is so important right now to scientists? 

 

Recent research by Terrie Williams and her team published in Science this week shows how vulnerable these magical and mystical creatures are in the face of impending doom (a.k.a. the gradual intrusion of humans into their previously isolated and secluded habitat). 

 

Heartbeat of a Narwhal: 

 

Williams used suction-cup devices that stuck to the narwhals for a few days, monitored diving physiology (including heart rate, stroke frequency and depth), then popped off and floated to the surface for retrieval. What she found was so strange that at first she thought the devices had malfunctioned, “I looked at it and the first inclination was to throw away the first five hours or so, because this isn’t normal diving response,” she said. “And then I realized, ‘Oh my gosh, this is a stress response — this is something very different, and very important.’”

 

Some Handy Definitions

A breakdown of some of the lingo.

 

Narwhal: These oceanic unicorns are real creatures, Monodon monoceros to be exact - a species of toothed whale or odontocete. One of their teeth in particular is pretty special, their upper-left canine tooth (of the males) grows about 8 feet from their jaw in a counter-clockwise spiral, forming the spectacular horn. They're found in the Arctic, around Canada, Greenland, Norway & Russia. 

 

Homeostasis: essentially, this just means stable conditions inside the body (temperature, pH, blood sugar, heart rate, blood pressure). The 'normal' settings inside your body are due to lots of regulators that adjust in response to external changes (e.g. your body temperature remaining stable)

 

Mammalian Dive Reflex: An evolutionary adaptation to help mammals survive the pressures of diving deep - this overrides usual homeostatic reflexes to change things like heart rate and blood flow and enable animals to hold their breath and survive huge water pressures

 

Bradycardia: Abnormally slow heart rate

 

In case you needed some more convincing, here's some beautiful photos by the absolutely incredible hero Paul Nicklen to help demonstrate just how amazing narwhals are: 

 

 

 

 

The Abstract 
"Until recent declines in Arctic sea ice levels, narwhals (Monodon monoceros) have lived in relative isolation from human perturbation and sustained predation pressures. The resulting naïvety has made this cryptic, deep-diving cetacean highly susceptible to disturbance, although quantifiable effects have been lacking. We deployed a submersible, animal-borne electrocardiograph-accelerometer-depth recorder to monitor physiological and behavioral responses of East Greenland narwhals after release from net entanglement and stranding. Escaping narwhals displayed a paradoxical cardiovascular down-regulation (extreme bradycardia with heart rate ≤4 beats per minute) superimposed on exercise up-regulation (stroke frequency >25 strokes per minute and energetic costs three to six times the resting rate of energy expenditure) that rapidly depleted onboard oxygen stores. We attribute this unusual reaction to opposing cardiovascular signals—from diving, exercise, and neurocognitive fear responses—that challenge physiological homeostasis."

 

So, basically... 

The narwhals hearts are being placed under extreme pressure, as a result of being entangled in nets. Usually when approached by a predator (like an orca), the narwhal would head for the depths, hiding under ice or in the shallows, and stay there quietly waiting until they're safe (a 'freeze response'). They're not built for speed.

 

What this study found was that activating their 'fight or flight' response set off both the frantic exertion of a 'flight' and the suppressed heart rate of a deep dive. Unexpectedly, the narwhal's heart rate is not responding to their swimming pace, as a result of the stress - they were swimming fast and deep, with extreme bradycardia. Essentially burning a lot of energy and oxygen, and severely stressing the heart muscle. 

 

“You had a heart that was only beating three to four beats per minute, and they were swimming in the hardest exercise that we ever see,” Williams said. “That’s why we called it a paradox. I’d never seen anything quite like it.”


This research has far-reaching implications for our magical monoceros friends, who are facing more and more threats as melting ice makes their habitats more accessible by fishermen and exploratory seabed miners. Increasing human activity could be inciting this stress response, and potentially causing long term negative health impacts. 

 

“My concern is for all of this exploration that we are doing around the world in terms of mineral resources off of coastlines,” she said. “I’m concerned that we just don’t know what the responses of these animals are.”

 

Solutions? 

Luckily for all us narwhal lovers, it's not too late. They're not currently listed as endangered, but we do need to learn more about them and there are things we can do to help protect their habitat.

 

Like all animals, and the entire planet right now, climate change and warming are having a negative impact. Depleting ice and food supplies, along with potentially altering currents, are all bad news for narwhals. In fact one paper ranked narwhals as more At Risk than polar bears from the impacts of climate change. The good news: as well as obvious things like being opposed to mining in the Arctic, there are lots of simple things you can do to make a difference. 

 

Changing up your diet (going vegan, or at least reducing your meat intake), switching your energy supplier, taking the bus more, will all help. I'd also highly recommend reading This Changes Everything by Naomi Klein for a realistic look at how to take on climate change. At the end of the day, changing some aspects of our lifestyle is a small price to pay in exchange for a world where something as incredible as a narwhal can still exist. 

 

 

 

The full journal article is available here: 

Paradoxical Escape Responses by Narwhals (Monodon monoceros) when Diving in a Seascape of Fear

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