科學(xué)家表示，響尾蛇已經(jīng)進(jìn)化出一種聰明的方法，讓人類誤以為危險(xiǎn)比他們想象的更近。

The sibilant sound of the rattlesnake's tail has long been a cinematic cliche.

響尾蛇尾巴發(fā)出的嘶嘶聲早已是大銀幕上的常用套路。

That tell-tale rattle is made by the rapid shaking together of hard rings of keratin at the tip of the creature's tail. Keratin is the same protein that makes up our fingernails and hair.

這種具有警示作用的咔咔聲是由該生物尾部末端堅(jiān)硬的角蛋白環(huán)一齊快速搖動(dòng)時(shí)產(chǎn)生的。這種角蛋白與構(gòu)成我們指甲和頭發(fā)的是同一種蛋白質(zhì)。

In this study, the scientists found a distinctive switch to a higher frequency as objects move closer to a western diamondback snake.

在這項(xiàng)研究中，科學(xué)家發(fā)現(xiàn)，當(dāng)有物體接近西部菱斑響尾蛇時(shí)，蛇尾發(fā)出的響動(dòng)聲會(huì)明顯切換到更高的頻率。

When human test subjects were exposed to this change in sound, they believed they were almost on top the snake, when in reality they were safely distant.

當(dāng)人類受試者暴露在這種聲音變化中時(shí)，雖然其實(shí)他們離蛇還有一段安全距離，但他們會(huì)以為自己幾乎就站在蛇的上方。

The scientists believe rattlesnakes evolved this trait because it helped them to avoid being stepped on by humans.

科學(xué)家認(rèn)為，響尾蛇進(jìn)化出這種特性是因?yàn)檫@樣可以幫助自己避免被人類踩到。

Despite this clever sound trick, hikers and walkers in the United States often find themselves in unwanted contact with these reptiles.

盡管響尾蛇有這種精明的聲音花招，美國的徒步旅行者和步行者還是經(jīng)常會(huì)意外遭遇到這些爬行動(dòng)物。

Rattlesnakes are responsible for the majority of the 8,000 people bitten in the US every year.

美國每年有8000人被蛇咬，其中大部分的罪魁禍?zhǔn)锥际琼懳采摺?

詞匯表

sibilant 嘶嘶作響的，此文指響尾蛇尾部搖動(dòng)時(shí)發(fā)出的聲音
cliche 老套的內(nèi)容
rattle 咔咔聲，短促尖厲的撞擊聲
keratin 角蛋白
frequency 頻率
exposed 暴露（在特定環(huán)境中）的
distant 遠(yuǎn)處的
evolved 進(jìn)化出了
reptiles 爬行動(dòng)物

閱讀理解：請(qǐng)?jiān)谧x完上文后，回答下列問題。

1. How do rattlesnakes make their sound?

2. In what way do rattlesnakes change the sound they make as objects get nearer?

3. What types of people in the US often encounter rattlesnakes?

4. How many people are bitten by snakes in the US each year?

答案  

1. How do rattlesnakes make their sound?
Rattlesnakes make their sound through the rapid shaking together of hard rings of keratin at the tip of the creature's tail.

2. In what way do rattlesnakes change the sound they make as objects get nearer?
Scientists found a distinctive switch to a higher frequency as objects move closer to a western diamondback snake.

3. What types of people in the US often encounter rattlesnakes?
Hikers and walkers in the US often find themselves in unwanted contact with these reptiles.

4. How many people are bitten by snakes in the US each year?
Around 8,000 people are bitten in the US every year.