A polar bear's journey

Nanu, a nine-year-old female polar bear, lives on the barrens of the Hudson Bay lowlands, south of Churchill, in the Canadian province of Manitoba.

Her den, which she dug into a creek bank, is nearly two metres in diameter and a half-metre higher than the exit tunnel. Air warmed by her body and breath rises into this upper space, bringing it to just below freezing. To save energy, she is able to lower her body temperature slightly from its normal 37 degrees C.

A mother who has not eaten for three months is able to nourish her cubs in utero and still keep her metabolism quiet enough to conserve energy for three more months of fasting. That’s because, in addition to her own considerable insulation—two inches of thick downy underfur combined with a full mantle of long, hollow guard hairs—every polar bear has a layer of fat below the skin. 

In December, in a state of suspended animation in her darkened den, Nanu delivers two blind, deaf, toothless, downy-haired young who are less than one percent of her size, with no body fat to speak of. The cubs, Siu and King, are immersed in the warm air trapped in the fur of Nanu’s belly. Mother’s rich milk, with 32 percent fat, not only keeps these helpless newcomers alive but allows them to thrive when temperatures outside can be as far below zero as their mother’s body temperature is above. 

At three weeks, the fine hair is replaced by a dense undercoat and longer guard hairs. By 25 days old, the soles of their little five-toed feet start developing hair as well, completing the insulation they need for moving around the den. 

Before their eyes open early in the second month, they learn to navigate with other developing senses, often with Nanu’s gentle guidance. They start to differentiate the textures, smells, sounds, and rhythms in the den. Their ears open by their second month, and their baby teeth come in. By their third month, they are able to raise themselves up on their hind legs in preparation for learning to walk.

The cubs go from one to two kilos in January, from two to four in February. By March, they are about 11 kilos and increasingly aware of their surroundings. 

The constant proximity of the three bears is creating a family bond that will see them through to separation and independence that is at least two years off.

Outside, the air is dry and supremely cold. The cubs may perceive the presence of a white fox outside the den rousting small mammals, like lemmings, that eke out a living in the tundra grasslands under the snow. One day, the piercing sound of a helicopter dropping grid stakes for a mining claim in the area startles the cubs, and they cluster back into Nanu’s bosom. 

By March the cubs are getting their lower incisors and canine teeth, and their hearing is becoming much more acute. They can now hear the fox walking over the den. And, as they pounce and roll together, they try out different voices and calls. 

With all this activity, Nanu must rouse herself from her sleepy state to scrape the frost that builds up on the walls and poke at the air vent. 

After the equinox on March 21, when the sun is visible for 12 hours, the days lengthen quickly. For the first time Nanu can see her cubs. Soon it will be time to get the three of them on their way to the bay, 70 kilometres away. 

There is nothing but uncertainty ahead, as there has been for every emerging mother bear since the beginning of time. But now, who knows? Will they be able to deal with the threats? 

By the end of March, Nanu is fully awake. The cubs, fearless little fur balls with claws and teeth, are ready to enter the wider world, a world where tradition and progress collide. Until very recently, the speed of change—whether in hunting traditions or in the seasons, the weather, the local conditions—was such that the bears could mostly adapt. 

With the onset of climate change, which has accelerated in lockstep with technological “progress,” change is happening much more rapidly than any plant or animal’s ability to respond. Nanu and the cubs are living in circumstances that at almost every turn will challenge their very survival. 

The adult bear who punches through the snow to the April sunshine is a scant 250 kilos, a shadow of her ample self. The cubs have gone from 1/500th of their mother’s weight when they were born to 1/20th of her current weight. Sunlight on crystalline snow drifts leaves them squinting as they tumble from the den. 

With just her head and shoulders hanging out of the exit, Nanu sniffs the air and scans slowly in all directions. Stiffly, she drags herself out of the den, shakes vigorously, and stands fully upright for the first time in five months. She heads up over the den, chuffing for the cubs to follow. Working her way to a gravelly ridge a few dozen yards uphill from the creek, she stands looking first one way and then another. Scanning the distance. Sniffing the air. She knows instinctively how vulnerable she and the cubs are. 

That first foray out of the den lasts no more than half an hour. Over the next week, Nanu and the cubs work their way up the ridge, stopping at a place where the wind has exposed alpine grasses. Nanu grazes on them to reduce her hunger and to reawaken her digestive system. 

Forays in these early days build and tone the cubs’ muscles for the journey that is about to begin. But these walks are also about readying Nanu’s own body for the long walk to the bay. 

Nanu decides it is time to move. In the 10 days since she opened the den, the sea has been there on the wind, particularly from the east. Silhouetted against the strengthening sun, the three bears walk away, the cubs roaming among Nanu’s feet, getting sidetracked, being called back. 

The route they are taking is similar to the one that Nanu first walked with her mother almost nine years ago. It isn’t long before they are crossing a pattern of ridges, each one a little lower in elevation than the previous one. 

The cubs play less now because when they are not walking or nursing, they are sleeping. Developing lungs take in new ground with every breath, building body awareness of place. The sun moves from in front to behind them as the days progress. For Nanu, they are familiar sensations from her memory, like melodies of a long-remembered tune. 

King will likely never come back this far inland. As a male, he will den during the winter. Siu, by contrast, will come here by heart, by the look and feel of the place—the ground-hugging spruce on the beach ridges, the faint smell of diesel from the trains running between the towns of The Pas and Churchill, the pungent dens of foxes—retracing the line they are etching in the snow. 

Suddenly Nanu stops with every muscle in her body flexed and ready. The cubs, too, tumble to a stop. Nanu sniffs and utters a high-pitched grunting sound that the cubs have never heard at that intensity. She stands and sniffs, first in one direction, then in another and another, finishing with a long stand facing downwind. In the distance, three gray wolves are making their way upwind. 

Encouraging the cubs to keep close, she stands again so that the wolves can see her before she takes a few vigorous running steps in their direction. She drops down and continues walking toward the wolves, cubs behind her. Driven by a mother’s combination of fear, caution, and courage, Nanu chooses to pose a threat of her own. 

Again, she stands, radiating the confidence of size. This time the wolves stop, look, and then look away. Suddenly they turn and lope off. For now, at least, the threat is gone. 

At this point in their lives, the cubs have no real capacity to run. Nanu won't leave them, except to fight on their behalf. The best she can do to protect them is to encourage the cubs to listen and to stay by. 

Day six, they crest a ridge. The cubs, riding on their mother’s back, sniff the air and sense that something is different. For the first time, Siu and King are smelling the odor of muddy ice on the foreshore flats of Hudson Bay. Mixed with the familiar scents are old oil, which may have washed in, and acrid plastic flotsam brought here by the slow rotations of Hudson Bay's waters. 

At the beach, Nanu breaks into a short canter. Stopping suddenly, she flops onto her back and rolls with her feet in the air and the cubs clambering all over her. She gets up, shakes and sniffs along a crack in the ice. She disappears momentarily down through the crack and reappears with a great tawny snake of bull kelp, full of alginates and fiber that will fill her digestive system and ready it for the meal to come. The little ones tire of it quickly and butt their way in for milk instead. 

They continue out onto the ice. Nanu stops and sniffs and stands much more often than she did while they were on the land. She and her cubs are entering a dangerous world of adult male bears. 

The threat from males is extreme. If they aren’t attacking a trio like this for nutrition in a lean year, then they are attacking the cubs to kill them, in the hope that this might bring the female back into heat. As hungry as Nanu is, she has to be ever vigilant. 

The voice of a raven and the squawks of a glaucous gull draw Nanu’s attention to a place far along a pressure ridge. She finds the remains of a ringed seal whitecoat. It is mostly just furry skin left behind by another bear, but she eats it and keeps moving along the crack. 

Suddenly she stops. She has located an aglu, a seal’s breathing hole in the ice. 

Nanu nudges Siu and King a few metres away and does her best with gestures, low chuffing sounds and gentle encouragement to get them to lie still while she moves back to prepare for the kill. 

With precision and care that seems to belie the size and strength of her paws, she scrapes away some of the snow covering the thin layer of ice on the inside of the lair. 

King is going to sleep, but Siu is soon back beside her mother. Nanu pushes Siu to her side and then, in a sitting position with her feet almost on what would be the apex of the dome of the aglu, she stiffens. Siu settles down quietly as well. 

Nanu can hear the quiet mewing of a baby inside the lair. But that is not the meal she is hoping for. Eventually, she feels a puff of condensed air come up through the air hole in the aglu, followed by the hollow swoosh of water below. Finally, the mother seal crawls up out of the water into her lair to nurse. 

In one smooth movement, forelegs braced, Nanu rises up and crashes down through the aglu, front feet followed by her head. Then, to Siu’s amazement, she recoils back above the surface of the ice with a seal four times the cub’s size. 

Nanu keeps her grip on the seal’s fragile head with her teeth. When it stops moving, she rips through the gray-silver fur and into the rich blubber that she has been craving. In no time, the cubs have started feeding on the carcass as well. Life on the ice has begun in earnest. 

From Ice Walker by James Raffan. Copyright © 2020 by James Raffan

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