Read Online The Great White Bear by Kieran Mulvaney - Free Book Online Page B
Authors: Kieran Mulvaney
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bear, never even knew that such a thing existed, but were nonetheless familiar with other things ursid, from a panda bear to a teddy bear, Yogi Bear to Gentle Ben, the moment you saw the face of a polar bear you would almost certainly know instinctively and immediately what type of animal it was. It is unmistakably...
bearlike,
with its rounded ears and furry muzzle. But compare the face of a polar bear to that of a grizzly and one difference is immediately apparent: the latter's seems flatter and wider, while the former's tapers into more of what might be called a Roman nose. The largest brown bear skulls are larger than the largest polar bear skulls; although they are in fact only marginally wider in relation to length than those of polar bears, they are also higher, creating more of a "dish-faced" impression than the more elongated visage of a polar bear. The more streamlined silhouette is accentuated by the neck, which in a polar bear is relatively long and slender, an adaptation that, in combination with the narrower skull, enables polar bears to succeed in hunting prey that would be beyond the reach of their evolutionary cousins.
"If a grizzly sticks its head in a seal hole," points out the San Diego Zoo's JoAnne Simerson, who has spent many years studying polar bears in captivity and the wild, "then it isn't going to be able to pull it back out."
And when a polar bear seizes a seal, the weapons it contains inside that elongated skull allow it to dispatch and dissect it with consummate efficiency.
Its forty-two teeth are significantly different in size, shape, and composition from those in a brown bear's jaw, and they are weighted far more heavily toward grabbing and holding prey and shearing meat. For example, the first premolars, the teeth immediately behind the pointed canines, are vestigial, effectively creating a gap between the canines and the molars that allows the former to penetrate deeply into seals and other prey without hindrance from adjacent cheek teeth.
The ears, too, are different from those of a brown bear. A grizzly's ears may not be its most prominent feature, but they are significantly larger than those of its nearest relative (while those of a sloth bear appear positively elephantine in comparison). The smaller the ears' surface area, the lower the amount of heat lost through them; and while losing heat is an occupational hazard of Arctic life, it is a danger to which a polar bear is tremendously well equipped to respond.
Any energy-conscious homeowner will agree that a sign of good attic insulation is a roof on which snow does not melt in winter. So it is with polar bears, the still-frozen snowflakes on their fur evidence that even as they maintain their core body temperature, which is almost identical to that of humans, the tips of their hairs may be as much as 75 degrees cooler.
By way of illustration of the effectiveness of polar bear insulation, Ian Stirling tells a tale of a fellow researcher who wondered if infrared photography could be used to detect polar bears on the ice, given that all warm bodies emit infrared radiation.
"To test the idea, he found a bear and took some pictures," Stirling wrote of his colleague. "The bear was so well insulated it gave off no detectable heat at all. But there was a spot on the infrared photo, just ahead of the bear's head ... made by its breath!"
So effective, in fact, is a polar bear at thermoregulation that even in temperatures that would threaten hypothermia in humans, its bigger concern is staying cool. This is the primary reason why its pace seems so unhurried: at temperatures betweenâ4°F andâ12°F, a bear's body temperature remains fairly constant when walking at about two and a half miles per hour; by the time it is moving at a mere four miles per hour, its body temperature may soar to 100°F. No wonder, then, that although adult bears are capable of bursts of high speed when launching surprise attacks on basking seals,
bearlike,
with its rounded ears and furry muzzle. But compare the face of a polar bear to that of a grizzly and one difference is immediately apparent: the latter's seems flatter and wider, while the former's tapers into more of what might be called a Roman nose. The largest brown bear skulls are larger than the largest polar bear skulls; although they are in fact only marginally wider in relation to length than those of polar bears, they are also higher, creating more of a "dish-faced" impression than the more elongated visage of a polar bear. The more streamlined silhouette is accentuated by the neck, which in a polar bear is relatively long and slender, an adaptation that, in combination with the narrower skull, enables polar bears to succeed in hunting prey that would be beyond the reach of their evolutionary cousins.
"If a grizzly sticks its head in a seal hole," points out the San Diego Zoo's JoAnne Simerson, who has spent many years studying polar bears in captivity and the wild, "then it isn't going to be able to pull it back out."
And when a polar bear seizes a seal, the weapons it contains inside that elongated skull allow it to dispatch and dissect it with consummate efficiency.
Its forty-two teeth are significantly different in size, shape, and composition from those in a brown bear's jaw, and they are weighted far more heavily toward grabbing and holding prey and shearing meat. For example, the first premolars, the teeth immediately behind the pointed canines, are vestigial, effectively creating a gap between the canines and the molars that allows the former to penetrate deeply into seals and other prey without hindrance from adjacent cheek teeth.
The ears, too, are different from those of a brown bear. A grizzly's ears may not be its most prominent feature, but they are significantly larger than those of its nearest relative (while those of a sloth bear appear positively elephantine in comparison). The smaller the ears' surface area, the lower the amount of heat lost through them; and while losing heat is an occupational hazard of Arctic life, it is a danger to which a polar bear is tremendously well equipped to respond.
Any energy-conscious homeowner will agree that a sign of good attic insulation is a roof on which snow does not melt in winter. So it is with polar bears, the still-frozen snowflakes on their fur evidence that even as they maintain their core body temperature, which is almost identical to that of humans, the tips of their hairs may be as much as 75 degrees cooler.
By way of illustration of the effectiveness of polar bear insulation, Ian Stirling tells a tale of a fellow researcher who wondered if infrared photography could be used to detect polar bears on the ice, given that all warm bodies emit infrared radiation.
"To test the idea, he found a bear and took some pictures," Stirling wrote of his colleague. "The bear was so well insulated it gave off no detectable heat at all. But there was a spot on the infrared photo, just ahead of the bear's head ... made by its breath!"
So effective, in fact, is a polar bear at thermoregulation that even in temperatures that would threaten hypothermia in humans, its bigger concern is staying cool. This is the primary reason why its pace seems so unhurried: at temperatures betweenâ4°F andâ12°F, a bear's body temperature remains fairly constant when walking at about two and a half miles per hour; by the time it is moving at a mere four miles per hour, its body temperature may soar to 100°F. No wonder, then, that although adult bears are capable of bursts of high speed when launching surprise attacks on basking seals,
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