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(22) What I'd like to discuss with you today is the polar bear. As I already mentioned on Tuesday, polar bears only live in the Arctic, primarily in northern Canada, northern Russia, and Alaska. If, for example, you are in southern Canada, you won't see any of these bears.
Now, you're probably aware that the Arctic is an extremely harsh environment and one of the coldest places on Earth. But let me remind you of what it's really like in the Arctic, especially in late December or early January. The temperature frequently drops below minus 40 degrees centigrade and sometimes gets even colder! Combine that with strong winds, little or no sunlight, and very little vegetation, and what you get is an environment in which very few species are capable of surviving. The polar bear, however, thrives in this kind of environment. The polar bear spends his time roaming throughout the Arctic, walking on land and ice, swimming in freezing sea water and floating on sheets of ice while looking for seals, fish, and other food. Their favorite food is seals, which they find along the edges of the ice, in holes in the ice, and under cracks in the ice.
Polar bears are much bigger than the brown and black bears. In fact, they're huge! They weigh up to 720kg. And they're designed to survive in their environment. (23) They have very thick, white fur, which helps them hide in the snow and ice and overcome the extreme cold. Polar bears are also strong swimmers. They have large front paws that amazingly allow them to swim a few hundred kilometers from land.
Despite their impressiveness, polar bears, unlike black bears, are an endangered species. (24) This is a result of global warming, which will be topic of our next film. The Arctic is becoming too warm for the bears. That ice I just mentioned to you is now disappearing! It breaks up much earlier in the spring, and now it's a lot further from land! Ice thickness in the Arctic has decreased by 40 percent in the last 30 years, and some scientists predict that the Arctic basin might not have any ice in another 50 years. For polar bears, this is terrible! (24/25) Ice is essential to their existence! Less ice means fewer seals and less food.
Polar bears do their hunting in the winter, but because the winter is getting shorter and because the ice is disappearing earlier, they have less time to restore their fat. In the summer, they're forced to remain on land for longer periods of time, and during that time, they live off the fat stored in their bodies. Thirty years ago, they spent just over three months on land. Now it's almost four months! This reduces their strength and energy. With less ice, polar bears must swim further to reach it. This further reduces their strength and energy. These circumstances have steadily decreased the bear population over the last 30 years.
22. Where can we see polar bears according to the lecture?
23. What can we learn about polar bears?
24. What made polar bears become endangered?
25. What will happen if there is less ice in the Arctic?
今天我想和大家讨论的是北极熊。如我在周二所说，北极熊只生活在北极地区，最初是在加拿大和俄罗斯北部，还有阿拉斯加。如果你住在加拿大南部，那你就不会看到北极熊。现在，你可能会想，北极地区环境恶劣，是地球上最冷的地方。但是我要告诉你真实的北极是什么样子的，尤其是在12月底和1月初。气温通常会降到零下四十摄氏度一下，有时会更低。再加上强风、极为稀缺的阳光和非常少的植被，这样的环境决定了能够在这里生存的物种数量极少。但是北极熊在这里生活地却很好。北极熊大部分时间都是漫步在北极的陆地和冰川之上，或者在冰冷的海水中游泳，或者在浮冰上寻找海豹、鱼或者其他食物。他们最喜欢的食物是海豹。通常在冰块的边缘位置、冰洞或者冰块裂缝下面能够找到它们。北极熊体型比棕熊或黑熊大得多。事实上他们体型巨大，重达720千克。造物主给了他们能在这种环境中生存的身体条件。它们长着厚厚的白毛，可以帮助它们在冰天雪地进行隐藏，还有助于它们克服极度的寒冷。北极熊还是游泳好手。它们巨大的前脚掌可能让它们游离海岸几百千米。虽然它们“天赋异禀”，但是北极熊和黑熊不同，它们现在已经成为了濒危动物。这是全球变暖带来的后果，这将是我们下次影片中的主题。北极地区的温度对于这些熊来说已经太高了。我刚才提到的冰正在消失！这些冰早春便开裂，现在已经飘离大陆很远了。在过去三十年里，北极冰层厚度减少了40%，并有一些科学家预言，50年后北极盆地内将不会再有冰。对于北极熊来说，这种情况非常危险！对于它们的生存而言冰是至关重要的！冰的减少就意味着海豹的数量减少和食物的减少。北极熊在冬天觅食，但是由于冬季时间的缩短和冰的消失，它们可以在体内储存脂肪的时间变短了。夏天它们不得不在陆地上待更长的时间，这段时间里它们就依靠体内存储的脂肪生存。三十年前，它们只需在陆地上待3个月。而现在将近需要4个月！这消耗了它们更多的体力和能量。而且，北极熊需要游更远才能找到逐渐减少的冰块。这又是对它们体力和能量的额外消耗。过去的三十年里，以上所有这些条件导致了北极熊数量的稳步下划。
22.根据以上讲座，我们在哪里能见到北极熊？
23.关于北极熊我们了解了什么？
24.什么使北极熊成为了濒危动物？
25.如果北极地区冰量减少，会发生什么？
译文属可可原创，仅供学习和交流使用，未经允许不得转载
