The Great White Bear Page 2

  Smaller floes he would simply nudge to one side or thump out of the way; with larger, more formidable adversaries, Sorensen demonstrated an entirely more sophisticated and subtle technique. He would head directly for one, slow down shortly before reaching it and perhaps even put the engine into reverse, relying on the ship's momentum to carry it forward, and ride the ship gently onto the ice. Then once more he would crank up the engine, powering the ship forward and pushing the floe out of the way, in the process frequently steering the ship hard to starboard or port so that as the ice began to move, the vessel would fall away into open water. As it did that, Arne would ease up on the throttle anew to prevent the ship, suddenly no longer meeting resistance from a huge chunk of ice, from rushing headlong into another.

  Initially, the ice edge encounter brought a rush of excitement to the Arctic Sunrise; crew interrupted watches and deck duties to lean over the bow and watch as Sorensen nudged small floes out of the way and slowly ground his way over and past larger ones. But as the afternoon unfolded, the ice became progressively thicker, and the bridge grew quieter as brows furrowed and focus sharpened. The percentage of water that was covered with ice now exceeded the percentage of water that wasn't, and ocean currents pushed floes into one another, compressing them, closing the ice into a mass that accumulated astern of us. Sorensen ascended to the crow's nest, affording him not only greater visibility but a separate set of steering controls, enabling him to look for leads through the ice and direct the ship toward them. The ship was enveloped in quiet, the scientific team peering keenly through binoculars in the hope of spotting marine life, the crew alternating between enthusiasm and uncertainty, the only noises the gentle throb of the ship's engines followed by a crash as the bow collided with a floe and the hull shook in protest at the force of the impact.

  The task was not aided by the evening descent of fog, combining with the day's diminishing daylight to restrict visibility at times to no more than thirty yards. The ship slowed to a crawl as pieces of ice loomed out of the mist like ghouls on a fairground ghost train. When finally the fog lifted, the sense of relief was palpable.

  "It is," observed the phlegmatic Sorensen, "so much easier when one can see where one is going."

  When the fog had lifted, the view before us was as different as it was now starkly beautiful, as if in its ascent the mist had peeled away the largest, most threatening floes, leaving in their place a dead calm sea, with nary a ripple, let alone any kind of swell to disturb its flat surface. Scattered about were innumerable smaller chunks of ice, many of them curiously misshapen and twisted, all of them now drifting harmlessly past. It looked for all the world like the detritus from an unseen tornado, a scene of terrible yet beautiful devastation, pieces of ice strewn randomly across the sea surface by the hand of God.

  We continued onward, north and west. Alaska receded far into the distance as we steamed into the waters of the Russian Arctic and closed in on our ultimate goal, the twin sentinels of Wrangel and Herald islands. Now we were certain we would find what we were looking for. Here, a combination of high latitude and the vagaries of ocean currents ensured that, even in late summer, sea ice was plentiful in thickness and extent. As a result, Wrangel and Herald combined to create a kind of polar bear paradise: a place where even under the harshest of conditions, the food supply was relatively plentiful and stable.

  We steamed slowly along, poking our way through floes, grinding along the edge of the fast ice that remained firmly attached to the islands' coasts and stretched for miles outward, as the islands themselves reached defiantly upward before disappearing into the fog. Dark clouds of sea birds swarmed through the skies. As the hull of our icebreaker rose up onto, and then cracked through, the ice in our path, schools of tiny arctic cod scattered rapidly, desperately searching for shelter. Here and there we spied ringed seals. Ahead of us, looming out of the mist, an occasional floe revealed itself to be packed tightly with walruses, seeking safety in numbers from the predator that always prowled nearby.

  And what a predator.

  Our crew was a hardened bunch, accustomed to being at sea for weeks or months at a time, used to seeing wildlife and landscapes known to most people only through television. But when, after weeks of slow-building anticipation and days of fighting through the ice, the call finally came from the bridge that a polar bear was up ahead, it prompted the instant dropping of tools or abandonment of food in a mad rush to the bow.

  This was a polar bear the way polar bears were meant to look: its fur thick and plush, its rump healthily rotund, its shoulders impressively muscular. It seemed not just to be walking across the ice but swaggering, as if surveying its kingdom and daring anyone or anything to encroach upon it. It carried, as only the most dominant predators do, the confident, almost arrogant bearing of an animal that felt no threat from fellow denizens in its kingdom. Its massive shoulders rolled with a self-assured poise reminiscent of an undefeated prizefighter.

  "Oh, yeah," said one of the crew admiringly as we hunkered down to shelter from a biting wind that had no evident effect whatsoever on our companion. "Look at him. He owns the ice."

  The bear seemed at first unaware of our proximity; but then it shuffled to the edge of the floe it was patrolling, sniffed the air, looked in our direction, briefly appeared to brace itself as if to jump into the water and swim toward us. It changed its mind, its ignorance of our presence evidently yielding to indifference toward it, turned around, and resumed its wandering, scratching at the ice, occasionally looking in our direction but mostly disregarding us as it continued on its way.

  That day, and in days subsequent, there were several more encounters, several more occasions on which the Sunrise cut back its engines and eased quietly along an ice floe as a bear sauntered confidently nearby, several more instances when work would halt as, transfixed, crew and scientists alike stood silently as they watched the scene unfold in front of them.

  At times it was hard not to imagine that greater forces of Nature were working to emphasize the rarity of the experience and the majesty of the animal at the heart of it. As if an unseen stagehand were operating a celestial spotlight, the sun abruptly shone on one bear just as we approached the floe that was its realm. Playing to the audience, the bear yawned theatrically and lay down, tucked its paws under its chin, placed its snout on them, and closed its eyes—occasionally opening them just a fraction to keep watch on the strange green iceberg in its midst. Then, receiving its cue from a director in the wings, it hauled itself to its feet, walked into a hollow in the ice, and posed for pictures with its front paws resting on the cavity wall.

  Most regarded our intrusion with mild curiosity or indifference. Others appeared resentful or even hostile. One marched away, looking repeatedly over its shoulder like a reproached dog. Another, uncertain what to make of the interloper yet unwilling to back down in the face of its enormity, stood its ground, bobbing its head and hissing at us in a combination of fear and ferocity.

  But then, unexpectedly, a bear would reveal a more vulnerable side. We slowed down, drifted to a halt, nosing into the ice as a bear lifted its head, sniffing the air and scenting our proximity. Slowly—not cautiously, but unhurried—it ambled toward us, curious as to the nature of the large object that had suddenly invaded its terrain. Above, seemingly unnoticed, a crew of thirty people leaned over the starboard bow, holding their collective breath and daring not to make a sound as the bear walked up to the hull, stretched its neck, sniffed, and all but touched its nose to the metal.

  Then there was a high-pitched beep and the click of a camera shutter, and at once the bear whipped away from us, racing back across the ice before slowing down, looking over its shoulder, and then continuing in a lumbering trot. It paused, looked back toward us now, sniffed the air again, and as if to reassure itself that a polar bear could not possibly truly have been frightened by anything so inconsequential, seemed almost to square its shoulders as it recovered its natural swagger.

  It strode up a smal
l hummock, looked briefly in our direction once more, then disappeared down the other side and was gone.

  Becoming

  In the dark, beneath the snow and ice, the cubs stir.

  It is almost spring in the Arctic, and the cubs are three months old. But they have yet to experience the warming glow of sunlight or the chill of the polar wind. The world in which they have spent the entirety of their short lives is a den hollowed out of snow, barely large enough to contain the cubs and the mother against whom they are curled tightly.

  She had been inseminated in May, fully ten months previously, a few weeks after she had entered heat and attracted the attention of most of the males in her vicinity. But insemination did not lead at once to pregnancy. The eggs, although fertilized, did not immediately implant.

  Once the cubs were born, the female would not eat for at least four months. So the eggs were held in abeyance while she readied herself for the onerous task that lay ahead; and in preparation for that task, she ate. More accurately, she gorged.

  In this she was aided by the forces of evolution, which had ensured that the time in which she would be seeking sustenance was a bountiful one, for spring in the Arctic is a veritable polar bear buffet. This is the period when the seals they eat are both most abundant and most vulnerable to predation, when ringed seal pups are born and, six weeks later, weaned. Upon weaning, each pup may weigh up to sixty pounds, forty-five pounds of which might be calorie-laden body fat. And, at this young age, not one of these corpulent morsels has learned to fear or avoid predators, leading to what noted polar bear researcher Ian Stirling has described as a "superabundance of fat, naïve seal pups that enables the pregnant females to accumulate fat so quickly."

  They need to. Later in the summer, the sea ice breaks up, the seal pups disperse into the water, and the smorgasbord is over. In some parts of the polar bear's range, for example, north of Russia's Wrangel Island, the feast may persist a while longer, the females continuing to hunt on the drifting pack ice even as it begins to break apart and drift south, until eventually the floes grind against the shore and the bears come onto land. Even then the respite may be brief, the bears needing to shelter only a few weeks before returning to the hunt when the sea freezes anew.

  At the other extreme, in Canada's Hudson Bay, the sea ice melts entirely by the end of July, forcing all the bears ashore. Because the ice does not form again until early November, they have no opportunity to hunt more seals before giving birth. As a consequence, a pregnant female in Hudson Bay may go eight months without any nourishment at all, almost certainly the longest period of food deprivation of any mammal on Earth.

  Under such circumstances, the obvious solution might seem to be for the eggs to implant, and the cubs to be born, as soon as the bears are forced to leave the ice. But however much (were they able to dwell on such matters) the pregnant females might wish it could be so, they must wait.

  They must wait to give birth so that the cubs are weaned in spring and not the depths of winter. And they must wait until the weather once more cools and the falling snow forms drifts large enough for them to fashion dens.

  The precise timing at which they do so varies according to geographical location and the vagaries of each year's weather conditions, but its approximate schedule remains relatively constant, following the path of winter's onset from north to south. In the Canadian Arctic, bears enter their dens on average by mid-September; in Alaska and northern parts of Svalbard (an archipelago north of Norway), they generally do so by mid-October; in more southerly parts of Svalbard, it is not until late October or early November.

  Not only pregnant females take shelter in dens, although they alone do so for the duration of the winter. Many other bears also seek refuge to avoid storms and extreme cold or heat, or when hunting is poor, particularly in the period after the sea ice breaks up and before it re-forms. It is a phenomenon seen less often in the High Arctic, where sea ice is generally available year-round, but observed with particular frequency at the southernmost reaches of the species' range, in Hudson Bay.

  There, when the sea ice melts in summer, bears come ashore en masse and hole up in earthen dens, where the temperature is cooler and bothersome insects are less likely to intrude. Most of these dens were excavated in eons past by ancestral bears; over time they have grown, and continue to do so, as a result of the bears' body heat gently melting the permafrost beneath the surface.

  Following the onset of fall and the return of the sea ice, males, females already with cubs, and females for which maternity is only a memory return to the hunt. Pregnant females that have also taken advantage of the topography, however, tarry a while, waiting until the drifting snow has covered their shelter to sufficient depth that they can tunnel into the drift and dig out a new den for the winter.

  At its most fundamental, construction of a maternity den requires drifted snow in which to dig a hole, and still-drifting snow that will cover up the hole and the bear that has curled up inside it. The first consideration for any pregnant female, says Thomas Smith of Brigham Young University (perhaps the foremost authority on denning behavior), is security: selecting a spot that minimizes the likelihood of exposure to or interactions with other bears. Cannibalism has been recorded in all three bear species in North America—Smith and colleagues have recorded it occasionally in polar bears—and a nursing female with cubs is potentially vulnerable to any kind of attack. Accordingly, whether they den on pack ice or on land, females invariably seek to avoid areas where males are actively hunting. But in addition to that one fundamental concern, there are subtleties and nuances that make some locales more preferable denning sites than others.

  Richard Harington, a polar bear biologist formerly with the Canadian Wildlife Service, found that in the Canadian Arctic, the vast majority of maternal dens face south. Prevailing winds from the north deposit greater amounts of drift, and, as with human housing, south-facing real estate is valuable in the polar bear world for its extra exposure to warming solar radiation. On Wrangel Island, in contrast, the distribution of dens follows no such discernible pattern; highly variable winds cause snow to build up on all sides of the island, making most areas suitable for denning.

  Indeed, Wrangel Island's sheltered, mountainous landscape provides ideal denning habitat. Other locations where drifts are easily formed—where there is an abundance of earth banks or hillsides, where there are valleys or mountains—boast a higher concentration of dens. Elsewhere, however, suitable spots are harder to find.

  Along the North Slope of Alaska, the terrain is fiat; snow is blown by unforgiving winds across the tundra, and bears must make use of drifts wherever they can find them. In many cases, dens are hollowed out of drifts as little as four feet high, nestled along coastal and river banks.

  Most dens are near the coast. In the Canadian Arctic, Harington found that 61 percent of dens were within five miles, and 81 percent within eight miles, of the shore, and a 1985 study found that most dens on Svalbard were no farther inland than two miles or so. The pattern is broken only in Hudson Bay, where the coastal plain is boggy and flat, and where females must sometimes trudge over sixty miles to find suitable terrain.

  The dens' proximity to shore provides easier access to the seals the desperately hungry mother will need to replenish herself when she and the cubs emerge in the spring. But some bears take this a step further and actually make their dens on the ice itself: either land-fast ice, which is attached to the shore, or even the drifting pack. A 1994 study of Alaska bears fitted with radio collars found that over half the dens those bears made were on sea ice—a high degree of ice denning that is not found anywhere else. It might be a consequence of the fiat terrain of northern Alaska making suitable sites on land relatively scarce, but Steven Amstrup of the United States Geological Survey (USGS), who has likely spent more time studying the polar bears of Alaska than anyone else, believes that the sea ice in the southern Beaufort provides a more solid foundation than is the case elsewhere.

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p; "Historically, the Beaufort Gyre circulated multiyear sea ice through the Beaufort Sea," he says. "That's ice that circulated through the Arctic year after year and kept getting thicker and thicker, so the sea ice in the southern Beaufort Sea had some of the most stable sea ice anywhere in the Arctic. It probably provided a very stable platform for polar bears to den on."

  Researchers elsewhere have concluded that denning on sea ice is infrequent and often limited to bears that could not make it ashore before the ice broke up. Understandably so, for making dens on the pack poses risks not experienced by those that choose to den on land. Ice floes shift, break up, re-form; they can turn over or raft under other floes with which they collide. The authors of the aforementioned 1994 study, among them Amstrup, saw six polar bears in pack-ice dens that were swept past Point Barrow, the northern tip of Alaska, and southwest into the Chukchi Sea because of unusually unstable ice conditions. The dens of two of the females had been destroyed when ice floes had collided and rafted onto each other; in their mouths the females carried tiny cubs. The researchers saw the mothers again later that spring; of the cubs, however, there was no sign.

  A pregnant bear knows instinctively and precisely what to look for in a denning site. She walks from snowbank to snowbank, testing each for consistency and depth, poking and prodding until she finds one that meets her criteria. She may travel many miles and take several days until she is satisfied with a location. Then, when she has found a spot she likes, she digs.