VOA慢速英语2013 As It Is - Nature:butterfly and how roosters know when to crow

（单词翻译）

As It Is - Nature:butterfly and how roosters know when to crow

Hi there. I’m Kelly Jean Kelly. Today on As It Is, we are talking about nature.

Specifically, about how roosters know when to crow, and one of the largest eggs the world has ever seen. But first, Caty Weaver¹ takes us to the Smithsonian Institution’s Natural History Museum in Washington, DC. Visitors to the museum have a rare opportunity to be surrounded by hundreds of living butterflies.

The Live Butterfly Pavilion is one of the Natural History Museum’s most popular exhibits. The Pavilion-- which, in this case, is a warm room -- is filled with flowering plants and 50 different species of butterflies.

“We have butterflies from Asia and from Africa, and South and Central America, and here in the United States.”

Dan Babbitt manages the exhibit. He says the butterflies are shipped from their native countries to the museum while they are in chrysalis state. That means they travel after they have built a protective covering around themselves.

“We unpack² them, we hang them up and wait for them to emerge until they’re a butterfly and then we’ll release them into the exhibit.”

One of the butterflies in the Pavilion is called a Blue Morpho, from the Amazon region of South America. It is the size of a person’s hand and has bright blue wings. Another is a black and red Asian butterfly called a Scarlet³ Mormon. One of them landed on nine-year-old Gunnar Bruce’s head.

“It’s just cool how the butterflies are all over. I feel like the butterfly really, like, likes me.”

Gunnar says he is enjoying learning more about butterflies.

“I learned that there’s lots of different kinds of species and that they only live for about three weeks.”

So is nine-year-old Ava Canales.

“I learned that when butterflies flutter when they eat, it’s because they can’t balance on the flowers.”

Exhibit manager Dan Babbitt says visitors also learn why butterflies are important to our environment.

“They will travel from flower to flower, taking pollen⁴ from one flower and depositing it into another, enabling that flower to be able to create seeds and disperse⁵. So we wouldn’t have a number of our flowers that we like to look at and fruit that we like to eat without the butterfly. Butterflies are also important as a food source, for a number of birds and other insects. They are either eaten as a butterfly or as the caterpillar⁶.”

But Mr. Babbitt says many butterfly species – such as the Monarch⁷ – are dying off.

“That’s something that we really need to watch out for and really focus on – the issues of deforestation and use of pesticides⁸ and just general land management issues, to make sure that we can provide for these butterflies. But also for all of wildlife and for us, to make sure that we have a healthy environment.”

He hopes the Live Butterfly Pavilion will help raise public awareness⁹ about the future of the butterfly.

I’m Caty Weaver.

We go now from a very quiet animal to a very loud one.

If you live near a rooster, you can depend on hearing him every morning when the sun comes up. But how do roosters know when it is time to crow? Christopher Cruise explains.

Japanese researchers say they have proof that an internal clock helps tell roosters when it is time to crow. That internal clock is often called a “Circadian rhythm.” It naturally links many plants and animals—including humans—with the Earth’s 24-hour cycle.

Researchers Takashi Yoshimura and Tsuyoshi Shimmura wanted to learn how Circadian rhythm works in roosters. Did they have an internal sense of what time it was? Or did they just react to the morning sun?

The researchers kept roosters in constant early morning light. Then they turned on their recorders so they could watch and listen.

The roosters crowed all day. But, they crowed the loudest first thing in the morning. The researchers believe this finding means that roosters naturally “know” what time of day it is.

However, the researchers also noticed that the roosters’ sense of time grew worse the longer they stayed in the experiment. The researchers say this observation suggests that external information, such as irregular light or the sound of other roosters, can weaken a rooster’s Circadian rhythm.

Mr. Yoshimura and Mr. Shimmura published their findings in the journal Current Biology. Mr. Yoshimura says scientists still do not know why a dog says “bow-wow” and a cat says “meow.” But, he says roosters can teach us more about genetically¹⁰ controlled behavior.

I’m Christopher Cruise.

And finally, we turn our attention to a giant egg in London. Christie’s Auction¹¹ House is selling a rare, fossilized egg from the extinct elephant bird.

Elephant birds lived in Madagascar, off the east coast of Africa. They were the largest birds ever to have lived. An elephant bird looked a little a lot like an ostrich¹². It was about three and a half meters high. elephant birds disappeared sometime between the 13th and 17th centuries. It is thought they were hunted to extinction¹³.

Experts with Christie’s say elephant bird eggs are even larger than dinosaur¹⁴ eggs. The one in London measures 30 centimeters high and 21 centimeters wide. That is about 120 times the size of an ordinary chicken egg. Christie’s will auction the egg in London on April 24. Officials expect that it could sell for more than $45,000.

That’s it for “As It Is” today.