- 
					But, as the human study suggests, another reason for dolphins keeping their eyes open during sleep is that they can look out for predators while asleep. 2017年6月六级真题(第三套)阅读 Section A
- 
					wild pigs attracted golden eagles from the mainland, and those flying predators crashed the fox population. 2018年12月六级真题(第三套)阅读 Section A
- 
					This idea is based on the principle that lions and other predators are far less likely to attack when they feel they are being watched. 2018年12月六级真题(第一套)阅读 Section A
- 
					Three-quarters of the world's flamingos fly over from other salt lakes in the Rift Valley and nest on salt-crystal islands that appear when the water is at a specific level一too high and the birds can't build their nests, too low and predators can move bri 2017年12月六级真题(第三套)阅读 Section C
- 
					When the water hits the right level, the baby birds are kept safe from predators by a corrosive ditch. 2017年12月六级真题(第三套)阅读 Section C