英语听力：2013-07-19 《恐龙的战争》3 顽强防御—15

 This tactic¹ is still used today on the plains of Africa. 

 

If you look at various species of plant eaters, they live together in groups, and if one of them spots a predator², they can whinny or hoot³ and let the rest of the herd⁴ know, so that they can keep on alert, or if the predators⁵ are right there, they can all break out into a run and run away from the attacker.

 

Parasaurolophus’ ability to communicate complex messages is a tremendous defensive⁶ advantage. Using its sensitive hearing, these creatures can detect a predator far off in the distance. They send out an alarm call to warn the herd. And even more effective, low-frequency sounds, with their long wavelengths⁷, travel much further than higher frequencies. 

 

These are kinds of sounds that can be transmitted over very long distances. 

 

This extremely low-frequency sound is called infrasound and can travel for kilometers.

 

You can produce a noise so low and so deep not only it goes through the air, it goes through the rocks and through the soil, and you pick it up in your feet. Elephants do that. Rhinos⁸ do that. Hippos do that. Crocodiles do that. Alligators⁹ do that. They produce infrasound. 

 

But for a Parasaurolophus, these calls can be used for more than just communication. Low-frequency infrasound can put up an aggressive form of defense¹⁰. 

 

Infrasound is a weapon. You can scramble¹¹ the brains of your enemy with a blast of infrasound. If you have 100 duckbills, 1,000 duckbills facing the same direction, producing high-decibel sounds, that’s a wave of energy that could knock over a predator or at least discombobulate it…

1 tactic   

n.战略，策略；adj.战术的，有策略的

参考例句：

• Reducing prices is a common sales tactic.降价是常用的销售策略。
• She had often used the tactic of threatening to resign.她惯用以辞职相威胁的手法。

2 predator   

n.捕食其它动物的动物；捕食者

参考例句：

• The final part of this chapter was devoted to a brief summary of predator species.本章最后部分简要总结了食肉动物。
• Komodo dragon is the largest living lizard and a fearsome predator.科摩多龙是目前存在的最大蜥蜴，它是一种令人恐惧的捕食性动物。

3 hoot   

n.鸟叫声，汽车的喇叭声； v.使汽车鸣喇叭

参考例句：

• The sudden hoot of a whistle broke into my thoughts.突然响起的汽笛声打断了我的思路。
• In a string of shrill hoot of the horn sound,he quickly ran to her.在一串尖声鸣叫的喇叭声中，他快速地跑向她。

4 herd   

n.兽群，牧群；vt.使集中，把…赶在一起

参考例句：

• She drove the herd of cattle through the wilderness.她赶着牛群穿过荒野。
• He had no opinions of his own but simply follow the herd.他从无主见，只是人云亦云。

5 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

6 defensive   

adj.防御的；防卫的；防守的

参考例句：

• Their questions about the money put her on the defensive.他们问到钱的问题，使她警觉起来。
• The Government hastily organized defensive measures against the raids.政府急忙布置了防卫措施抵御空袭。

7 wavelengths   

n.波长( wavelength的名词复数 )；具有相同的/不同的思路；合拍；不合拍

参考例句：

• I find him difficult to talk to—we're on completely different wavelengths. 我没法和他谈话，因为我们俩完全不对路。 来自《简明英汉词典》
• Sunlight consists of different wavelengths of radiation. 阳光由几种不同波长的射线组成。 来自辞典例句

8 rhinos   

n.犀牛（rhino的复数形式）

参考例句：

• There are many reports of people taming and even training Indian rhinos. 有许多关于人们驯养甚至训练印度犀牛的记载。 来自辞典例句
• The rhinos had fed during the night in the rice fields of these villagers. 犀牛夜里在这些村民的庄稼地里也已吃饱了。 来自辞典例句

9 alligators   

n.短吻鳄( alligator的名词复数 )

参考例句：

• Two alligators rest their snouts on the water's surface. 两只鳄鱼的大嘴栖息在水面上。 来自辞典例句
• In the movement of logs by water the lumber industry was greatly helped by alligators. 木材工业过去在水上运输木料时所十分倚重的就是鳄鱼。 来自辞典例句

10 defense   

n.防御，保卫；[pl.]防务工事；辩护，答辩

参考例句：

• The accused has the right to defense.被告人有权获得辩护。
• The war has impacted the area with military and defense workers.战争使那个地区挤满了军队和防御工程人员。

11 scramble   

v.爬行，攀爬，杂乱蔓延，碎片，片段，废料

参考例句：

• He broke his leg in his scramble down the wall.他爬墙摔断了腿。
• It was a long scramble to the top of the hill.到山顶须要爬登一段长路。