英语听力：探索发现 2013-02-27 猛玛象进城记 Mammoths to Manhattan—13

The owls can raise anything from 1 to 12 chicks in a summer season. To survive, their young will have to quickly learn to negotiate the dangers of city life. Longer hunting trips are sometimes necessary as open land disappears. But so long as the cit

英语听力：探索发现 2013-02-24 猛玛象进城记 Mammoths to Manhattan—12

And farming fuelled the growth of another habitat, one that would become an even bigger challenge to North America's wildlife. The modern city was born. The city is an artificial environment, built around the needs of millions of people, and yet it a

英语听力：探索发现 2013-02-22 猛玛象进城记 Mammoths to Manhattan—11

At first, the Europeans relied heavily on local food supply by native people. But as they settled in, their farming practices began to shape the landscape of North America. The plow allowed them to farm larger areas of land, helping to feed the expan

英语听力：探索发现 2013-02-20 猛玛象进城记 Mammoths to Manhattan—10

Where purple martins had once laid their eggs in hollow threes, in time, they came to rely almost totally on people to provide nests for them. These artificial nests were made from dried out squashes known as gourds. The shape made them perfect nesti

英语听力：2013-03-15 猛玛象进城记 Mammoths to Manhattan—20

Its also a prime hunting ground for red-tailed hawks. And they have the perfect nesting site right next to it. Theyd moved in on the top floor of this expensive Manhattan apartment block. It acts like a surrogate tree, supporting their large nest. Th

英语听力：2013-03-13 猛玛象进城记 Mammoths to Manhattan—19

Its incredible that so many birds cram into the tiny spaces underneath the bridge. But the battle for living spaces is now an everyday fact of city life. The most populated North American city is New York. Here space is a precious commodity with more

英语听力：2013-03-17 猛玛象进城记 Mammoths to Manhattan—21

This may look like a safari through the African savanna. In fact it's a theme park in Florida. And it allows people to experience a world outside their own. In some ways, they are visiting a land from another time. 14 thousand years ago, large parts

英语听力：2013-03-20 恐龙之战之极限生存 Extreme Survivors—1

In a world of terrifying creatures, being small means facing danger at every turn. If you were a small animal, the late cretaceous would have been an awful time to be around. For a youngster, every day is a struggle to stay alive. Their only chance i

英语听力：2013-03-22 恐龙之战之极限生存 Extreme Survivors—2

I think its a very beautiful idea that you have this little egg thats surprisingly small and out of it comes a baby sauroposeidon thats about the size of a rabbit and in two or three decades, its gonna be a 50-ton adult. But why does this huge animal

英语听力：2013-03-24 恐龙之战之极限生存 Extreme Survivors—3

Its reputation for violence and terror is unmatched, but an infant T-Rex comes into the world better protected than most. If you say Tyrannosaurus Rex, I think of gentleness. I think of superb motherhood and a struggle to raise ones chicks. The dread

英语听力：探索发现 2013-02-17 猛玛象进城记 Mammoths to Manhattan—9

By the mid 1800s, the horse and the cowboy had come to symbolize the wild west. And of course, with the cowboys came cattle. As the bison quickly vanished from the landscape, cattle filled their place. Meanwhile increasing numbers of the tame horses

英语听力：探索发现 2013-02-15 猛玛象进城记 Mammoths to Manhattan—8

Just over 500 years ago, Europeans arrived in North America. And with these colonizers came an animal that hadnt been seen here for thousands of years. The horse returned to the Americas, now tamed and carrying the Spanish conquistadors. This new for

英语听力：探索发现 2013-02-13 猛玛象进城记 Mammoths to Manhattan—7

...and may trace their ancestry all the way back to the first dogs to enter North America. The Carolina dogs are pack animals with a strick hierarchy topped by an alpha male. Like most wild dogs, they hunt in groups. But many of the kills they make a

英语听力：探索发现 2013-02-08 猛玛象进城记 Mammoths to Manhattan—5

But there is a problem with the idea that hunting caused the mass extinction. Mammoths were not the only animals to disappear. Camels survived for millions of years in North America, but disappeared around the same time as the mammoths. Wild horses f

英语听力：探索发现 2013-02-06 猛玛象进城记 Mammoths to Manhattan—4

The same signs appear in young male mammoth tusks, but those living in North America at the end of Ice Age laid down their stress rings three years earlier than usual. In other words, it seems that young males were leaving the herd at an earlier age.

英语听力：探索发现 2013-02-03 猛玛象进城记 Mammoths to Manhattan—3

But even on its own, a mammoth was still highly dangerous and an attack required stealth and teamwork. One of the hunters may have acted as a decoy, distracting the animal while others surrounded it. These hunters had another trick up their sleeve. U

英语听力：探索发现 2013-02-01 猛玛象进城记 Mammoths to Manhattan—2

To find the answers, we need to rewind history around 14,000 years to a time when the first people set foot in North America. The continent was about to undergo a profound change, a change these new arrivals may have played a part in. Throughout the

英语听力：探索发现 2013-01-30 猛玛象进城记 Mammoths to Manhattan—1

Downtown L.A., the ultimate modern American city, but Los Angeles skyscrapers are built over the graves of thousands of extinct Ice Age beasts. Today all we have are memorials to these vanished animals, but imagine if they had survived into the prese

英语听力：探索发现 2013-01-27 冰河新新州 Ice Age Oasis—20

Though very powerful, shes not a sprinter and she needs to get close to her prey before she strikes. This time shes run too soon and its a fruitless chase. Then her attention is diverted to a slower-moving target, slow but not defenseless. She backs

英语听力：探索发现 2013-02-10 猛玛象进城记 Mammoths to Manhattan—6

Saber-tooth died out, but another big cat survived. The puma may have been more able to adapt because its diet is more varied and includes small prey. The grizzly bear also lived through the post Ice Age changes and now thrives in North America. Once