英语听力：自然百科 探索世界奥秘之Wild Africa - Deserts(浩瀚沙漠) Unit02（在线收听）

In this barren sea of sand, it's harder for larger animals to find enough to eat. You've got to be a real specialist, like the Namib sand snake. By sidewinding, it can swim its way up the dunes. But in such an open arena, ambush is tricky, it's speed that counts. The wedge-snouted lizard can afford to be blase. It has a secret weapon, rocket propulsion. Then it's under the sand as fast as you can , the best place to escape predators and the sun.

Here in the Namib, shelter is sparse. What little there is, is fiercely protected. Colonies of dune ants monopolise the tough Namib grasses. Though aggressive to most invaders, the ants do tolerate the presence of small sap-sucking bugs which they get to milk for precious sugary water. In their grassy home, the ants are shaded from the worst of the sun. But out on the surface of the sand, the temperature can reach a blistering 60 Celsius.

Spoor spiders have an extraordinary survival strategy. With nowhere to hang their webs, they spin their silk on the ground, meshing sand grains together. The result: a mini blanket which serves as a sunscreen. But these sandy blankets do more than shelter. They are beautifully camouflaged sticky traps.

Dune ants get most of the food they need on their doorstep. But to supplement their diet they must also venture out onto the sand. Their long legs lift them above the baking ground to where the temperature is slightly cooler. But they must still tread carefully, it's a minefield out there. 

propulsion:the force that drives a vehicle forward 推进力

monopolise:to have complete control over something so that other people cannot share it or take part in it 垄断 独占

camouflage:the way that the colour or shape of an animal protects it by making it difficult to see in the area in which it lives 伪装 拟态