to hunt for insects in the forest outside. 在森林外围捕食昆虫

91. They're totally dependant on the digested remains of food that's brought here from outside.
    它们完全依赖的食物消化残渣 都是来自于外界
92. Each evening in just two hours
    每天傍晚 只是前后2小时内
93. three million bats leave the safety of the cave
    300万只蝙蝠一起离开安全的洞穴
94. to hunt for insects in the forest outside.
    在森林外围捕食昆虫
95. But not all will return.
    但并非所有的蝙蝠都能返回
96. As they leave the cave
    蝙蝠离开山洞后
97. the stream of bats form a doughnut-shaped ring.
    即在空中组成一个面包圈一样的队列

来自《行星地球 第一季 第四集 Planet Earth S01E04 洞穴》第 94 行