听力文本

This is the biggest underground river passage in the world,
这是世界上最大的地下河通道
so big a jumbo jet could fly through it.
大到可以通过一架大型喷气式客机
It's Deer Cave in Borneo.
它就是婆罗洲的鹿洞
The sheer size of Deer Cave allows some animals to gather there in huge numbers.
鹿洞的容量很大，使得大批动物到此聚集
A staggering three million wrinkle-lipped bats live here.
这里住着数量惊人的300万只犬吻蝠
The bats roost high on the walls and ceilings,
这些蝙蝠倒挂在洞壁和天顶上
where they're well protected from the outside elements and safe from predators.
它们在此完全不受外界因素的干扰，还能躲开天敌。

And while they're up here, the bats produce something very important.
它们高悬在洞穴上方时会产生一种非常重要的东西
This 1 00-metre-high mound is made entirely of bat droppings, guano.
这堆100多米高的东西全都是蝙蝠的排泄物，粪便。
Its surface is covered by a thick carpet of cockroaches. Hundreds of thousands of them.
地面上爬满了密密麻麻的蟑螂。它们的数量无以为计。
Caves are one of the few habitats on Earth not directly powered by sunlight.
洞穴是地球上少数几种不直接依赖阳光的生态环境之一
In the absence of plants, this food chain is based on a continuous supply of bat droppings.
在缺少植物的情况下，这里的食物链完全依赖供应不断的蝙蝠粪便
The cockroaches feed on the guano and anything that falls into it.
蟑螂的食物就是粪便以及任何掉进里面的东西。

词汇解析

1.roost on 栖息；停留
Birds roost on the trees.
鸟儿栖在树上。

2.in the absence of 缺少…时
In the absence of any contrary agreement, the firm accepts full liability.
因为不存在任何相反的协议，该公司承担全部责任。

视频及简介

洞穴是不受阳光控制的生物栖息地之一，但这并不意味着那里就不存在野生生物。本集节目将深入洞穴内神秘而永恒的黑暗，探索山洞、洞穴和隧洞中未知的地下世界。