英语听力：探索发现 2012-12-12 美洲大平原 American Serengeti—20

This trail leads to the cave and the freshly dead bison, just out of reach. Hunger makes the bear risk everything. He falls and joins the bison in its tomb. Now he can eat his fill. but after that there's no way out. ln time he'll be just one more ic

英语听力：探索发现 2012-11-28 美洲大平原 American Serengeti—14

13,000 years ago, the ice age cheetah was the pronghorn's greatest enemy. And pronghorn would have needed all their amazing speed. The American cheetah was larger than its African cousin. But it had the same Achilles' heel. A cheetah's high-performan

英语听力：探索发现 2012-11-30 美洲大平原 American Serengeti—15

Larger than any lion alive today, this would have been an awesome predator. These caves were probably its winter den. With such abundant game down on the plains, this hunter's life must have been pretty good. Sheer size and power and the benefit of l

英语听力：探索发现 2012-12-02 美洲大平原 American Serengeti—16

So let's go back in time, back 13,000 years to relive one day in the life of North America's great ice age plains. It's early morning at the end of a long, hot summer. Even major rivers are beginning to run low. Colombian mammoth herd follows the riv

英语听力：探索发现 2012-12-07 美洲大平原 American Serengeti—18

The scene is set for a daily ice age drama. Only the very largest are safe now. Patience is the key, the lionesses close in, waiting for their opportunity. The first charge causes chaos, but this is just what the lions want. ln the melee, they've alr

国家地理-2008-08-21 鸵鸟蛋·豺狼·秃鹰

Here we are on the Serengeti Plain in Africa, where an ostrich has abandoned an egg and a hungry jackal means to make a meal out of it. What weve got here is a highly motivated animal trying and failing to figure out this culinary conundrum. Its jus

英语听力：自然百科 鸵鸟蛋·豺狼·秃鹰

Here we are on the Serengeti Plain in Africa, where an ostrich has abandoned an egg and a hungry jackal means to make a meal out of it. What weve got here is a highly motivated animal trying and failing to figure out this culinary conundrum. Its just

英语听力：自然百科 大迁徙 Great Migrations—2

What on earth could drive this headlong rush to slaughter? Only earth herself with her insistent clocks. This story begins in the Great Rift Valley, where the continent is tearing itself apart and being reborn. The plains in the shadow of the rift, t

英语听力：探索发现 2012-11-02 美洲大平原 American Serengeti—3

Even the mastodon is buried here, a long dead relative of modern elephants. This was once a bear, but not like any bear in North America today. Claw marks gouged into the cave wall showed the bear was not killed direct by the fall. It made a desperat

英语听力：探索发现 2012-11-04 美洲大平原 American Serengeti—4

The death throes of the last great ice age left a signature that we can read today. These giant potholes were left behind by blocks of buried ice that melted, leaving hollows that later filled with water. For thousands of years since then, they've be

英语听力：探索发现 2012-11-07 美洲大平原 American Serengeti—5

Mud from the ancient riverbanks is good for building nests. lt also holds more evidence that will help us to reconstruct the ice age past. Every now and then,new clues surface, hinting at what else might lie beneath. ln this dried-up pond in South Da

英语听力：探索发现 2012-11-09 美洲大平原 American Serengeti—6

The site was once a spring-fed pond, full of water. Mammoths were tempted in to drink. But when they tried to climb back out, the banks were steep and slippery. Just like the short-faced bear imprisoned underground, some became trapped. Scavengers wo

英语听力：探索发现 2012-11-11 美洲大平原 American Serengeti—7

The store of pollen paints a picture of the plains of 13,000 years ago, a picture that looks very different from the open prairie grassland of today. But why did this region look so different back then? The ice sheets to the north, although retreatin

英语听力：探索发现 2012-11-14 美洲大平原 American Serengeti—8

The Osage orange seeds were carried far across the plains, before being deposited, pre-packed in their fertilizer growbags, ready to take root. As the ice age waned, the milder climate and the mixed vegetation meant the plains were able to support a

英语听力：探索发现 2012-11-16 美洲大平原 American Serengeti—9

Bison calves are born in summer and can run within a few hours of their birth. They have no choice. The herd won't wait in its eternal quest to find new grazing. Smaller grazers are still found here, too. But they stay put instead of wandering the pl

英语听力：探索发现 2012-11-18 美洲大平原 American Serengeti—10

Colombian mammoths had to feed almost round the clock to fuel their bulky bodies. But as the ice age ended, food was not the mammoths' biggest problem. A new and deadly predator began to infiltrate the plains, a match for any prey, even the mighty ma

英语听力：探索发现 2012-11-23 美洲大平原 American Serengeti—12

Because these two bull mammoths both had broken tusks, they could have fought at closer quarters than they would do normally. Twisting and turning, they became locked in a deadly embrace. Even more bizarre, this twist of fate then caused a third fata

英语听力：探索发现 2012-11-25 美洲大平原 American Serengeti—13

A lone wolf weighs as much as four coyotes, but one on one it's still no match for a bison. Wolves, though, live and hunt in packs of up to 15 and when they launch a cooperative attack, they're devastating. First they get the bison on the run, then f

英语听力：探索发现 2012-10-28 美洲大平原 American Serengeti—1

Denver International Airport is coming to life and about to receive the first arrivals today. By midnight, more than 1,500 aircrafts wouldve touched down here, delivering tens of thousands of people to this modern metropolis. But when did people firs

英语听力：探索发现 2012-10-31 美洲大平原 American Serengeti—2

As North America emerged from the grip of the last ice age, the door was opened to outsiders for the very first time. As these early immigrants pushed their way south, they found themselves in a land of an unimaginable opportunity, overflowing with g