Bare necessities life for the polar bear
The animal was wearing a radio collar, fitted two years previously to log her movements. Water temperatures ranged from 2 to 6° C. The bear survived, but her cub, swimming with her, disappeared. Nor did the mother’s journey end when she reached the pack ice. She travelled a further 1,800km, walking and swimming. Recaptured, her weight had fallen by 22%.
Polar bears hunt around sea ice. When this melts, they retreat onto land. Only the females hibernate, giving birth to their babies. In late spring and early summer, both sexes head northwards. The cold, oxygen-rich waters of the Arctic abound in fish, food for ringed and bearded seals. These are eaten by bears. The seals surface for air at holes in the ice. A polar bear’s sense of smell is legendary; it can detect the breath of a seal kilometres away. The great white predator homes in on the odour and waits beside the ice hole. When a seal surfaces, it is seized and dragged to its death.
With the onset of global warming, the ice-cap is receding at an alarming rate. Nobody knows how far polar bears swim, but they are being forced to cover longer distances. A bear emaciated after a long journey will hunt less successfully than one in good condition. Starving individuals, too slow to catch seals, may attack walruses in desperation. Walruses are slow-moving and easy for a bear to approach, but their formidable tusks are lethal.
Unless it can obtain enough food to restore its strength, the prospects of a female breeding successfully are low. Cubs born to underweight mothers are less likely to survive. But the record-breaking swim in the Beaufort Sea illustrates an even more intractable problem; adults may be able to swim huge distances, but their youngsters can’t. Mothers often swim with tired cubs on their backs.
The polar bear is a European species. Travel from Ireland to the northernmost tip of Iceland and you’ll be just below the Arctic Circle. Go as far north again, veering slightly to the east, and you’ll reach Svalbard. This Norwegian archipelago supports about 3,500 polar bears. Stragglers have come as far south as the Norwegian mainland and the odd one turned up in Iceland, where it was shot. Bears are said to have visited Scottish islands during the Little Ice Age, the cold spell that gripped Europe between the 17th and 19th centuries. There is no record of one coming as far south as Ireland.
The world’s largest land carnivore has the dubious distinction of being the only man-eating animal left in Europe. It’s a dangerous beast. The brown bears of forests and mountains sometimes kill people. There were 18 deaths during encounters with them in the Carpathians between 1990 and 2000. But these incidents arose from human meddling rather than bear malice. They mostly involved hunters or poachers approaching bears they had injured, or shepherds trying to protect their livestock. A brown bear will attack if it’s cornered, or if a mother is separated from her cubs. Although it will fight, it doesn’t want to eat you. Only a polar bear will do that.
Despite its size and ferocity, the polar bear is a vulnerable creature. A Johnny-come-lately in evolutionary terms, it developed from the brown bear a mere 150,000 years ago. It can still interbreed with its brown cousin and produce fertile hybrids. Such a highly specialised animal can’t easily alter its lifestyle and so it’s vulnerable to rapid environmental changes, such as those resulting from global warming.
About 25,000 polar bears survive in 19 sub-populations. The five polar nations signed an agreement on hunting in 1973. This has stabilised numbers, but now declines are being recorded again. If the polar ice-cap melts completely in summer, as some climate models suggest, how will the bears fare?
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