Why we need to protect polar bears
Climate change poses a mounting danger to polar bears, and were they to vanish, the effects would reach well beyond the Arctic itself. Few animals are so precisely suited to the punishing cold of the far north, where the thermometer can sink to around -40°C. Part of what makes this possible is a layer of fat, in places almost ten centimetres thick, sitting just beneath the skin. Carry a comparable amount of such tissue and a human being would be classed as obese, with diabetes and heart trouble the probable result — and yet none of these afflictions touches the bear.
Some light was thrown on this puzzle by research that Reidar Solheim and his team published in 2015. Setting the animal's genetic make-up against that of the brown bear — a warmer-climate cousin and the polar bear's nearest kin — the group was able to pin down the genes behind the species' survival in so harsh a place. Among these was APOB, a gene that drives down concentrations of low-density lipoproteins, or LDLs, the so-called 'bad' cholesterol. Because it is faults in this very gene that raise a person's heart-disease risk, the polar bear could prove a valuable model for studying that condition in ourselves.
There is a second disorder the bear's genome might help resolve, one that falls most heavily on the elderly: osteoporosis, in which the bones grow less dense — a decline brought on, as a rule, by too little exercise, a shortage of calcium, or plain starvation. Bone is not fixed tissue; it is forever being rebuilt, laid down or broken down according to how well an animal is nourished and how much strain the skeleton must bear. Every pregnancy, though, puts the female polar bear through an ordeal. When autumn arrives she hollows out a den in the snow and stays inside for the whole winter, giving birth there and remaining with her cubs. Roughly six months of going without food follow, during which she must sustain both herself and her young from her own dwindling stores of calcium and energy. Her bones, remarkably, stay every bit as dense and strong.
In 2009 the physiologists Marika Toft and Elias Brandt offered a way of making sense of this contradiction. What they found was that a bear, before ever beginning her den, would build extra density into her bones in advance; and that when she came out half a year later alongside her cubs, no meaningful thinning of the bone could be detected. Brown bears passing the winter in hibernation lack this trick, and are left to rebuild their skeletons wholesale once spring returns. Should the way polar bears remodel their bone ever be worked out, the gains might extend to astronauts, and to the many patients confined to their beds.
For all that such medical promise should weigh in any argument for conservation, it ought not to be the whole of the case. Our instinct is to shield the creatures we credit with intelligence and feeling — elephants, say, or the primates — whereas the bear tends to strike people as dull-witted and, more often than not, aggressive. Reports from the field tell against that picture, hinting among other things at a real talent for solving problems. At the Nordvik Arctic Centre, a male bear named Sisu was repeatedly seen turning a branch into a lever, working it to bring down a fish that had been hung beyond his reach. The same knack, if less strikingly, has turned up in the wild: one male, in a calculated bid to reach a researcher stationed on a platform three metres above him, took a run-up and hurled himself onto a row of barrels.
Further work — an investigation carried out by Johanna Kreft in 2010, for one — has caught the animals in bouts of careful, purposeful handling of objects. Bears in her study would gather items into heaps and then topple them, for all the world as if the whole thing were a sport. Behaviour of this kind, she argues, is nimble and thought-through, and it points to reserves of creativity and problem-solving that the species had never been given credit for.
Emotion, too, shows through, though here again the proof is only anecdotal. A bear that has just let a kill slip away will often lash out at the surrounding ice and snow, apparently in annoyance. Stranger still are the bonds the animals sometimes strike up with other species — romping, for instance, with the sled dogs of the Arctic. One polar bear reared by hand, a female called Luna, grew so attached to her keeper, Tomas Reinholt, that the two of them will even swim side by side — astonishing behaviour, given that wild polar bears are quite prepared to hunt human beings.
Were the warming climate to drive the species out of existence, we would forfeit not just the medical advances they may yet make possible but, more grievously, a magnificent and clever animal.
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Question 1 - 7
Choose TRUE/FALSE/NOT GIVEN
1.
Polar bears are extremely well suited to surviving in very cold conditions.
True
False
Not given
2.
A polar bear's thick fat causes it to become diabetic.
True
False
Not given
3.
Solheim's team compared the polar bear with a close relative from milder surroundings.
True
False
Not given
4.
Defects in the APOB gene have been found to cause heart disease in brown bears.
True
False
Not given
5.
A female polar bear will leave her den at intervals over the winter months to feed.
True
False
Not given
6.
Female polar bears increase how dense their bones are before constructing a den.
True
False
Not given
7.
Brown bears do not need to restore their bones once winter ends.
True
False
Not given