The male bear moves with an easy rolling gait through the wind-scoured ice in northern Svalbard; at a distance, he is all but invisible against the white background. This is exactly the point – the bear isn’t actually white. The transparent guard hairs scattered light, while his black skin absorbs any sunlight that reaches him at such high latitudes. Scientists call him ursus maritimus — “the sea bear,” and he is the largest living land carnivore. On average, adult males weigh between 300 to 800 kilograms and reach lengths of 2.0 to 2.5 metres nose-to-tail. Females typically weigh about half as much (150 to 300 kilograms), and are also smaller than the males. One of the most obvious differences between the two sexes is the shape of their heads and shoulders – males have broader heads and more massive shoulders.

Compared to brown bears, the body form is leaner, the neck longer and flatter head. These features will help the bear to slip under water and push its head into seal breathing holes. That marine life shows up in every detail. A layer of blubber (fat) can be up to 11 centimetres thick beneath the fur and backed by a dense undercoat. The paws are enormous (typically 30 centimetres across), with hair on their soles which provide good grip over both ice and snow. The claws remain short and curved and are designed to hook onto seal skins rather than to dig roots. Due to spending so much time on the frozen ocean surface rather than on land, polar bears were officially classified as marine mammals. Their world circles around the north pole through five countries: Canada, the u.s.a. In Alaska, Greenland, Norway, and Russia. There are 19 recognised sub-populations of polar bears which follow the seasonal cycles of sea-ice.

Some bears stay near shore-fast ice during winter. Other bears travel thousands of km’s drifting along floes from the Beaufort Sea towards Siberia. When summer melts the platform they rely upon for hunting, many come ashore and wait until the following spring when conditions improve. Seals make waiting possible. Ringed seals and bearded seals supply most of the calories required by the bears. Most often still-hunted, a bear locates a seal breathing hole, finds a position down-wind of the hole and waits motionless for several hours until a seal surfaces for air. Once it has done so, the bear strikes, dragging the seal onto the ice where it eats off the blubber first. Sometimes the rest of the seal carcass goes to Arctic foxes and gulls. Walrus, belugas, carrion birds and eggs fill gaps in diet — however fat-rich seal blubber provides the fuel that allows female polar bears to nurse cubs through long fasts.

Polar bears reproduce according to the calendar of ice formation/thaw. Mating takes place in April/May; the fertilised egg does not implant till autumn. In October or November a pregnant female digs a maternity den into a snow-drift — either on land or on stable pack ice. One or usually two blind cub-bears are born in December or January — each weigh less than 1 kg. The mother doesn’t eat or drink inside her den for months — converting her own fat into milk. The family emerges from the den in March/April and the young ones remain with her for approximately 2½ years — learning where to find holes and how to read the condition of the ice.

Estimates of numbers vary greatly over such a large habitat — however the i.u.c.n. Classifies polar bears as vulnerable — with global estimates of approximately 22,000–31,000 animals. Not all sub-populations are doing equally well. The Southern Beaufort Sea group located off Alaska/western Canada declines as ice-free seasons get longer. The greatest long-term pressure is climate-driven loss of sea ice — which reduces hunting time and forces bears ashore where they experience greater human contact, poorer nutrition, lower survival rates amongst cubs. Pollution and industrial activity add stressors — and the u.s.a. Lists polar bears as threatened under their Endangered Species Act.

Most wild polar bears live for 15–18 years — although some females do survive into their late twenties. In zoos they can live beyond thirty years. They can swim steadily for hours — have been tracked covering distances exceeding 100 kms without stopping — and can smell a seal nearly 1km away. For millennia Inuit communities who have lived beside them have considered nanook a figure of respect and caution woven into stories, hunting practice and names associated with places.

Watch that same male again as day turns to night — he stops before a pressure ridge tests the air then drops flat beside a dark hole — he will wait. The bear, the seal and the ice have conducted this dance together for at least 120 thousand years. What changes now is how long the platform remains intact each year after melting in spring