英语听力精选进阶版 7190（在线收听）

Background: 虎鲸，俗称杀人鲸，本是非常善于交流的物种。不过最近，英国圣安德鲁斯大学的研究人员发现，虎鲸在捕食过程中不发出任何声音，以确保不被猎物发现。

Killer whales whistle to talk to each other and click to find their way around. It's the echoes from these clicks that help the animals to map their surroundings and to pinpoint the location of their next meal.

But while one type of killer whale eats fish, the other hunts marine mammals, including seals and porpoises. A shoal of salmon can't hear the clicking of an approaching killer whale, but the mammals, with their highly sensitive underwater hearing, can.

The researchers used underwater microphones to listen to killer whales hunting seals off the coast of Alaska. They found that the animals fell completely silent when they were hunting. But, somehow, they still managed to organise themselves into groups - often spreading out up to a mile apart, before coming back together and calling loudly to each other while they shared their catch.

The scientists now hope to attach satellite trackers to individual killer whales, to find out more about this stealthy behaviour.

Glossary 词汇表

whistle 吹口哨 

echo 回声，共鸣 

surroundings （周围的）环境或事物 

to pinpoint 准确地找出或确定（位置） 

mammal 哺乳动物 

shoal 大量，许多，一大群鱼 

to fall silent 安静下来 

to spread out 分散 

catch 猎物 

stealthy 隐秘的，鬼鬼祟祟的

Questions and Answers

1. Why do whales whistle to each other? 

Researchers believe that it helps the animals to become familiar with the area where they are swimming and find their prey.

2. List some of the animals killer whales eat. 

You could have mentioned: fish, seals and porpoises.

3. How have scientists found out how killer whales hunt? 

They used underwater microphones to record killer whales while they were hunting seals.

4. How do researchers hope to find out more about how killer whales behave? 

They intend to attach satellite trackers to individual animals.