科一科二 · 科二
Zipping, Zapping, Zooming Bats
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When the sun goes down, bats come out to hunt. You have to look quickly to see a bat before it's gone.
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Many bats hunt insects. They eat lots of insects. Each night a bat chomps half its own weight in bugs. If you weigh 60 pounds, that's like eating 125 peanut-butter-and-jelly sandwiches every day. Don't be scared if á bat flies past your head. It won't get into your hair. It's probably catching a juicy mosquito.
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Bats are terrific hunters. A little brown bat can catch 150 mosquitoes in 15 minutes. The gray bat can gobble 3000 insects in one night. Bracken Cave in Texas is home to 20 million Mexican free-tailed bats. Together they munch 250tons of insects every night. Bats help get rid of insects that bite people. Bats also zap moths, beetles, and grasshoppers. These insects eat farmers' crops, the food that you and l need.
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Bats are good hunters because they have a special way of using sound. Bats make high beeping sounds. These sounds are too high-pitched for our ears, but bat ears can hear things ours can't. The beeps go out from the bat in waves. The sound waves hit objects around the bat. When sound waves hit an object, they bounce back. The bounced sound waves come back to the bat as echoes. The bat can tell by the echoes what kind of insect is near, and exactly where it is. Then the bat can catch it. We call this echolocation.
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The echoes that bounce off a tree sound different from the echoes that bounce off a bug. Bats use echolocation to " hear” things that are in their way, They can zoom fast through dark forests and black cave tunnels. If a bat gets into your house, open a door or window. The bat will echolocate, and " hear" the opening it can use to fly out.
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