英語時間｜Are bats blind?【603期】
發佈時間：00:00 2021-12-16 HKT
We are often told that bats use sounds to‘see’, and that they are actually blind. There is even an English idiom‘blind as a bat’, that means not being able to see well. However, bats are not blind at all – and according to some standards, some bats even have better eyesight than humans!
It is true that many bats use sounds to‘see’. This kind of perception has a special name called‘echolocation’, which means knowing one's location by the use of echoes. The principle is quite simple: bats send out sounds, and from the reflected sound waves, they know the distance between themselves and an object in front of them. This prevents them from bumping into objects or walls. However, some bats use their eyes instead of echolocation when needed.
Take, for example, the various species of fruit bats. Many of them drink nectar from plants instead of hunting insects（hence why they have‘fruit’in their name）. And if they drink nectar, they do not use echolocation at all. These species have very sharp vision, and some of them can even see ultraviolet light, which means that their vision is even better than humans’as we cannot see ultraviolet.
There are at least 1,300 different species of bats all over the world. Some feed off flowers, some eat insects, and three species（all from Latin America（拉丁美洲））drink blood. With such different food needs and living environments, it is natural that they may have different ways of ‘seeing’ things.
Vocabulary
blind as a bat (idm) 視力欠佳
echolocation (n) 回聲定位
echo (n) 回聲
principle (n) 原理
nectar (n) 花蜜
ultraviolet (adj) 紫外綫的
圖：資料圖片
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