Narwhals are, in every respect, utterly bizarre. They were the source of seaborne legends for centuries, as sightings of them were taken to be close encounters with sea monsters, and their long tusks were often sold as unicorn horns by disingenuous merchants for ridiculous prices. Even without all that, though, they’re amazing creatures.
Excluding the massive tusk, they reach around 5.5 metres in length, and can weigh anything up to 1,600kg. They can dive as deep as 1,500mand stay down for 25 minutes at a time, hunting for benthic sea creatures like wolf fish, skate, halibut and armhook squid. They also hunt closer to the surface for fish like polar cod and Arctic cod.
They are, in every sense, specialised polar hunters, especially considering that their migratory pattern leaves them in frigid water almost all year round. For this reason, they are extremely well protected again the cold. 40% of their total mass is blubber, allowing them to maintain a steady temperature constantly in conditions that would kill other marine mammals if they stayed for too long, as well as granting them better buoyancy.
Their size also works to their advantage, or, rather, their surface area does. Despite how big they are, narwhals have a relatively low surface area, a smooth overall shape which lowers resistance and allows them to retain more heat through metabolism. Their tail is only very narrowly connected to their body, meaning they can use it to propel themselves without using up too much energy.
Because they’re so well adapted to the cold water, they do most of their eating in the winter months, opposite to most other migratory Arctic animals. During the summer they move out of the icy open ocean and closer to the coast to congregate, breed and raise calves.
Similarly to penguins, seals and other kinds of whale and porpoise, narwhals have counter current heat exchangers in their flippers, meaning that warm blood entering is cooled by the cold blood leaving. In this way, the warmth is all retained in their bodies and they don’t lose any heat from their outer extremities. When the water is warmer, the efficiency of this adaption can actually be reduced.
When they deep dive, they have a whole arsenal of other adaptions which come into effect, both against the increasing cold and the building pressure around them. They enter a state similar to torpor, only more functional, via bradycardia. Their hearts slow down far beyond a normal rate, until only their vital organs and swimming muscles are functioning. This way, loss of energy is reduced as much as it can be, enabling them to stay down longer, withstand the adverse conditions of the deep sea, and then return further function when they reach the bottom so they can hunt without having to deal with so much fatigue.
Callum is a film school graduate who is now making a name for himself as a journalist and content writer. His vices include flat whites and 90s hip-hop.