There are about 1,200 species of bats in the world, Swartz says. Some eat fruit. Others eat insects or nectar(花蜜). And just a few drink blood.
Some bats use their eyes to see where things are .Others collect information about their surroundings by bouncing sound off objects and listening to the echoes.
But what all bats have in common (other than being the only flying mammals in existence) are flexible wings that enable them to change directions quickly. If you’ve ever seen bats darting(猛冲)through the air at dusk ,you probably noticed how abruptly they could change directions.
Scientists have long assumed that bats fly the same way as birds and insects do ---with rigid, airplane-like wings that hinge at the shoulder. The problem with that assumption, however, is that bats aren’t birds or insects. As mammals, they have more in common with people, horses,and dogs than with other flying creatures.
For example, birds have hollows bones, and insects have no bones at all. But most mammals have solid and heavy bones, which could make flying tough.
To solve this problem, bats have evolved strong and heavy bones near their shoulders, where they need more support. They’ve also saved some weight by developing lighter and weaker bones near the tips of their wings. The result is light but strong and very flexible.

There are about 1,200 species of bats in the world, Swartz says. Some eat fruit. Others eat insects or nectar(花蜜). And just a few drink blood.
Swartz 说全球有约1,200种蝙蝠。一些以蝙蝠水果为食，一些以吃昆虫或花蜜为食 ，吸血的只少数。
Some bats use their eyes to see where things are .Others collect information about their surroundings by bouncing sound off objects and listening to the echoes.
一些蝙蝠使用眼睛看清东西在何处，其它是通过从物体反射声音及听回声来收集他们的周围的信息。

But what all bats have in common (other than being the only flying mammals in existence) are flexible wings that enable them to change directions quickly. If you’ve ever seen bats darting(猛冲)through the air at dusk ,you probably noticed how abruptly they could change directions.
但蝙蝠有个共同点（不是说它们唯一现存的飞行哺乳动物。译者注：这儿插上“不是说它们是唯一现存的飞行哺乳动物”这么一句话让人觉得突然，可能是因为人们经常以为它们唯一现存的飞行哺乳动物，所以这里突然冒出这么一句话来），也就是他们有可折叠翼（这是动物学是专业名词，也可以直接译为柔软、灵活易曲的翅膀），使它们能够快速改变方向，如果你在黄昏时分见过蝙蝠在空中横冲直撞，你就也许注意到它们改变方向是多么突然。
Scientists have long assumed that bats fly the same way as birds and insects do ---with rigid, airplane-like wings that hinge at the shoulder. The problem with that assumption, however, is that bats aren’t birds or insects. As mammals, they have more in common with people, horses,and dogs than with other flying creatures.
科学家们长期以来一直认为，蝙蝠与鸟及昆虫的飞行方式是一样的，即以僵硬的、机翼似的、铰链般长在肩上的翅膀进行飞行。然后这种看法的问题是，蝙蝠既不是鸟也不是昆虫。作为哺乳动物，它们与人类、马、狗（这些哺乳动物）的共同之外要比与其它飞行生物的共同之处多。
For example, birds have hollows bones, and insects have no bones at all. But most mammals have solid and heavy bones, which could make flying tough.
比如，鸟有中空的骨头，昆虫根本就没有骨，而大部分哺乳动物都有坚固而又沉重的骨头，这就使得飞行变得很困难。
To solve this problem, bats have evolved strong and heavy bones near their shoulders, where they need more support. They’ve also saved some weight by developing lighter and weaker bones near the tips of their wings. The result is light but strong and very flexible.
为了解决这一问题，蝙蝠在其肩部附近区域进化出强壮且沉重的骨头，因为这肩部需要更多的支撑。蝙蝠还通过在其翅膀的尖端长出比较轻且强度要弱一些的骨头使它们减少了不少的重量。结果是他们不但变轻了，而且更强壮与灵活了。