英语听力：2012-02-17 从南极到北极 From Pole To Pole—14（在线收听）

 All across southern Africa, all animals are journeying for the same reason. Buffalo join the great track. Nowhere else on Earth are so many animals on the move for the same urgent purpose. They are all heading for the swamps of the Okavango, a vast inland delta. At the moment it is dry. But water is coming. The travelers are hampered by dangerous dust storms. Mothers and calves can easily get separated from the main herd. For this pair, sanctuary lies in a patch of woodland a few miles ahead. They can’t rest until they reach it. The main herd has already got there safely. Finally, the strugglers emerge from the dust. The exhausted calf is still blinded by sand. Its mother does everything possible to help it.