听力原文

Though the swifts depend on the cave for shelter, they never stray further than the limits of daylight, as their eyes can't see in the dark.
尽管雨燕依靠洞穴遮蔽，他们却必定在日落前归巢，因为他们的眼睛无法在黑夜中看清事物。
However, deep inside the cavern, other creatures are better equipped for subterranean life.
然而洞穴深处是一群更适应地下隐秘生活的居民。
A colony of bats is just waking up, using ultrasonic squeaks to orientate themselves in the darkness. Night is the time to go hunting.
一群蝙蝠刚刚醒来，他们运用超声波在黑夜中确定自己的方位。夜晚是狩猎时间。

重点讲解

重点讲解：
1. depend on
依靠；依赖；
eg. Nora grew accustomed to depending on her husband...
诺拉变得习惯于依赖丈夫。
eg. Many farmers have to depend on subsidies to make a living wage.
许多农民的基本生活工资要靠补贴来维持。
2. a colony of/colonies of
（鸟、昆虫或动物的）群体，集群，群落；
eg. A colony of gulls inhabits the island.
一群海鸥栖息于这个岛上。
eg. The Shetlands are famed for their colonies of sea birds...
设得兰群岛以其众多的海鸟而闻名。
3. wake up
醒；醒来；
eg. Jake wanted to wake up, but sleep held him back.
杰克想要醒来，但睡意使他又沉入梦乡。
eg. You wake up one morning and things have switched places.
当你早晨醒来的时候，可能一切都变了。