英语听力：探索发现 2012-09-09 长毛象王国 Mammoth—1

21st century, North America, where people have reached even the remotest corners of the continent, and pushed back the boundaries of modern technology. But it isnt so long since humans first set foot here about 14,000 years ago. And back then, North

英语听力：探索发现 2012-09-12 长毛象王国 Mammoth—2

By searching for evidence that still survives today, we reconstruct the landscape and the wildlife of prehistoric North America. During the last Ice Age, massive glaciers covered half of North America. But to the far northwest, there was a land that

英语听力：探索发现 2012-09-14 长毛象王国 Mammoth—3

The Yukon and its neighbor, modern-day Alaska, were once part of the land that was Beringia. Stunning though this region is today is just a shadow of the world that was encountered by the First Americans. Underground, the soil is frozen solid, as it

英语听力：探索发现 2012-10-19 长毛象王国 Mammoth—18

Away from the herd, the dominant male mammoth is distracted from his usual routine, today he has a more urgent priority than food, a younger challenger that wants to take his place. This ritual clash of tusks will decide the future for them both. The

英语听力：探索发现 2012-09-16 长毛象王国 Mammoth—4

Of all these creatures, the woolly mammoth is the undisputed symbol of the Ice Age. But what do we really know about how this giant lived. How did it use its massive spiral tusks? Modern-day elephants, the mammoths closest living relatives, may provi

英语听力：探索发现 2012-09-21 长毛象王国 Mammoth—6

In one remarkable discovery recreated here, the head and hide of a large carcass was exposed a unique opportunity for scientists to tap some Ice Age secrets. The remains were of an extinct steppe bison, a longer-horned relative of the North American

英语听力：探索发现 2012-09-23 长毛象王国 Mammoth—7

Bears have long claws, but they get worn down by the daily grind, moving around and rooting for food. They are just not sharp enough to rip into the bisons hide. To solve this puzzle, we need to look to Africa. African buffalo are similar in size to

英语听力：探索发现 2012-09-26 长毛象王国 Mammoth—8

The answer lies in the effects of North Americas immense and fluctuating ice sheets. As they grew, they locked up so much water that the sea levels began to fall. The Bering Sea between Asia and North America began to drain away, leaving a bridge of

英语听力：探索发现 2012-09-28 长毛象王国 Mammoth—9

This is Alaska today, a wetland of forests, boggy tundra, lakes and rivers rivers that still churn out fresh clues to the Ice Age past. This is a brick-sized tooth, and it belong to a woolly mammoth. Its narrow ridges of enamel tell us more about how

英语听力：探索发现 2012-09-30 长毛象王国 Mammoth—10

The fact that both horses and mammoths were here suggests these forests werent. It seems that, 14,000 years ago, Beringia was a huge expanse of open grassland. This unique habitat of cold, dry grasslands is known as mammoths steppe. But thats not how

英语听力：探索发现 2012-10-03 长毛象王国 Mammoth—11

At its maximum, the ice covered nearly six million square miles. And in places, it was up to two miles thick. The ice blanket was punctuated only by occasional islands of rock, the peaks of the very highest mountains. Though Beringia itself remained

英语听力：探索发现 2012-10-07 长毛象王国 Mammoth—13

Small ears also help to minimize heat loss, the opposite effect of those huge heat-dispersing ears of their relatives, African elephants. Other Beringia animals have more than a fur coat to help them cope with cold. This skull belongs to the bizarre-

英语听力：探索发现 2012-10-10 长毛象王国 Mammoth—14

Arctic ground squirrels hibernate like other small mammals, but with a unique twist. They can lower their body temperature right down to almost minus 3 degrees centigrade. But thanks to a biochemical super-cooling process, they dont actually freeze.

英语听力：探索发现 2012-10-12 长毛象王国 Mammoth—15

For these baby animals, it was a race to grow up over the brief summer to be tough enough to face the winter. One young animal that died in its first winter was discovered in the permafrost of an Alaskan gold mine. Recreated here are the best-mummifi

英语听力：探索发现 2012-10-14 长毛象王国 Mammoth—16

But back then, they had serious competition from the giant short-faced bear. The short-faced bears bone chemistry reveals it was a carnivore and up to a ton, probably the largest meat-eating mammal that ever walked the earth. On its long legs, it ran

英语听力：探索发现 2012-10-17 长毛象王国 Mammoth—17

Musk oxen and arctic hares are well-insulated against the cold as are the largest grazers of them all, the woolly mammoths. This herd is regrouping, ready for a long day feeding on the grasses beneath the snow. Mothers need to keep milk flowing for t

英语听力：探索发现 2012-10-21 长毛象王国 Mammoth—19

They huddle and turn to face the threat, a giant short-faced bear. Faced by a wall of horns, the bear moves on to sniff out a less daunting meal. Occasional blizzards are another harsh reality of living in Beringia, but the drifting snow may at least

英语听力：探索发现 2012-10-05 长毛象王国 Mammoth—12

The male flicks the air with his tongue to test if the ewe will accept him. The next stage of courtship is not so subtle. He gives her a kick. At this highly-charged time of year, skirmishes can easily erupt between the rams, especially if they both

英语听力：探索发现 2012-10-24 长毛象王国 Mammoth—20

One giant short-faced bear is more than a match for two lions. But in this bitter climate, lions cant afford to go without a meal for long. A mammoth calf in its first winter is a tempting sight. But mammoths are attentive mothers and they have the b

英语听力：探索发现 2012-10-26 长毛象王国 Mammoth—21

The lions will have to try elsewhere. Could a bison be a more realistic prospect? The wind whips up again offering cover, and the hunters focus on a target on the fringes of the herd. Before long the carcass freezes and becomes difficult to eat. Aban