時差N小時:北極熊是怎樣保持冷靜的呢?

If you found yourself instantly transported to thefreezing arctic, your first concern would be keepingwarm. But what about the animals that make theirhomes on these vast fields of ice and snow? Do polarbears need to worry about freezing to death?

如果你發(fā)現(xiàn)自己突然置身于天寒地凍的北極，你首先考慮的事情是保暖。但是在這片白茫茫的冰天雪地上興建家園的動物們會怎么辦呢?北極熊會擔心被凍死嗎?

Actually, a polar bear's biggest problem is keepingcool, not keeping warm. Thanks to its thick coat offur, its tough hide, and a four inch layer of blubber,a polar bear is extremely well insulated. Indeed, if a resting polar bear is photographed withinfra-red film—a kind of film which can measure the amount of heat escaping from a body–thepolar bear won't even show up at all. That doesn't mean polar bears are as cold as thesurrounding ice; their normal body temperature is about the same as ours.It simply meansthat polar bears retain their body heat very well. In fact, a polar bear can rest in a pit of icysnow, at temperatures as low as minus thirty-four degrees Fahrenheit, without needing to burnany extra fat for warmth!

實際上，北極熊面對的最大問題不是保暖，而是保持冷靜。在厚厚的毛發(fā)，堅硬的熊皮和厚約四英寸的脂肪層的保護下，北極熊能夠極好地防止熱量流失。事實上，如果用紅外感熱膠片(一種可以測量從體內流失的熱量的膠片)拍攝一只休息中的北極熊，可能根本看不到它的存在。這并不說明北極熊像周圍的冰雪一樣冰冷，它們的正常體溫跟人類一樣。這只能說明北極熊可以很好地保存身體里的熱量。北極熊可以躺在溫度低到零下34度的雪坑里休息，而且不需要燃燒額外的脂肪來取暖。

While this insulation is great for keeping warm, it can lead to some serious overheating. As aresult, polar bears don't like to run after their prey. Chasing a seal at only four and a half milesan hour, a polar bear's temperature climbs to a feverish hundred degrees. It may have to lieon its back with its feet in the air to cool down. Polar bears prefer to hunt by waiting near a holein the ice, and letting dinner come to them. It's the best way to conserve energy, and keepcool, in the Arctic north.

雖然與外界絕緣能保持體溫，但也會導致體溫嚴重升高。因此北極熊不喜歡追逐獵物。北極熊在追逐一只時速4.5英里的獵海豹時，身體會變得炙熱，體溫升高到100度。它不得不四腳朝天仰躺著使身體冷卻下來。北極熊更喜歡守株待兔，它們在冰窟附近等著獵物上鉤。在北極，這就是即能保持體力又能冷靜下來的最佳方法。