英語聽力文摘 自然界的鬧鐘

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Cock-a-Doodle-Do

It’s four A.M. You’re tucked safely into a warm bed, savoring the last few hours of sleep before daybreak. And then, suddenly… (a rooster crows).

It must be time to wake up, roll out of bed, and tend to the farm. Except it’s four A.M., it’s still dark out, and you’re not a farmer.

It’s that neighbor of yours, the one that for some unimaginable reason keeps a rooster as a pet. A rooster that flaunts the most basic rules of neighborhood etiquette by crowing every morning before sunrise. What gives?

Most people assume that roosters are programmed to crow at the first sign of sunlight to announce the dawning of a new day, or some such romantic notion.

Like all birds, roosters call in a daily cycle determined by circadian rhythms. That is, a rooster’s internal clock allows it to anticipate the sunrise and prepare for another exciting day of looking for food.

But why must roosters crow as they prepare to start their day, and why do some roosters sound off before dawn? Roosters are territorial creatures and don’t much like other roosters trespassing on their land.

They crow in order to establish their domain and warn other roosters to stay away or prepare to brawl. And because their internal clocks are sometimes set a bit early, some roosters begin crowing well before sunrise.

早上四點(diǎn)，你還在溫暖的被窩里蜷著，享受著天亮前為數(shù)不多的睡眠時間。此刻卻聽到雄雞打鳴……

聞雞起“床”，爬出被窩，開始農(nóng)作。但是，現(xiàn)在才四點(diǎn)!外面黑咕隆咚的，而且，你又不是農(nóng)民。

公雞是隔壁家的，因?yàn)槭裁措y以理解的緣由把公雞當(dāng)做寵物。每天的黎明前，公雞都會打鳴，仿佛問候鄰居早安。這是為什么呢?

大多數(shù)人認(rèn)為公雞每當(dāng)?shù)谝豢|陽光照耀大地，就按規(guī)律打鳴，提示嶄新一天的開始。另外，還有很多浪漫的解說。

和其他鳥類一樣，生理節(jié)律決定了公雞每天都要打鳴。也就是，公雞的生理鐘讓它期待日出，積極地為新的一天覓食。

但是，為什么公雞會打鳴呢?而且偏偏是在黎明前呢?公雞有領(lǐng)地意識，自己的領(lǐng)地“決不許其它公雞侵犯”。

公雞以此來維護(hù)自己的領(lǐng)地，警告其它公雞遠(yuǎn)離，否則一場爭斗難以避免。又因?yàn)楣u的生理鐘有時候設(shè)置得早一些，所以，一些公雞打鳴在日出前。