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True to their name, boa constrictors squeeze the life out of their prey. But how does a boa know it's snuffed out a rat? The snake listens for a heartbeat. When it stops, that's the cue to let go, according to a study in the journal Biology Letters.
蟒蛇可是名副其實的獵物殺手。但蟒蛇是怎么知道它們已經成功殺死了一只老鼠？原來，蟒蛇會聽老鼠的心跳。當老鼠心跳停止了，它們就會放松緊纏著老鼠的身體。這項研究發表在《生物學快報》雜志上。
Researchers outfitted rat cadavers with artificial beating hearts. They used dead rats to control for other signs of passing, like muscle spasms. Then they warmed up the rats, set the hearts pumping, and dangled them in front of hungry boas.
研究人員人工控制死鼠的心跳。他們用人為控制的死鼠肌肉痙攣來表現老鼠已經死亡。然后，他們把死鼠的身體弄熱，安裝上人造心臟泵，再把死鼠放在饑餓的蟒蛇面前。
The snakes attacked. And as long as that rat heart kept thumping, the boas kept tightening their coils and applying bursts of pressure, sometimes for more than 20 minutes. But as soon as scientists killed the heartbeat, the boas loosened up.
蟒蛇開始攻擊了。只要老鼠的心臟還在不停跳動，蟒蛇就不斷收緊身體并一陣陣地用力纏繞，有時超過20分鐘。但是，一旦科學家讓死鼠停止心跳，蟒蛇就會松開身體。
Even captive-born boas who'd never hunted live prey paid attention to the pulse—suggesting the behavior is innate. And for good reason. The authors say constriction takes a lot of energy. And it can be dangerous, say, if an enemy strikes while the snake's coiled around its quarry. But by following the telltale heart, boas can keep the pressure on just long enough. Before a relaxing meal.
即使圈養長大的、從來沒有獵殺過鮮活獵物的蟒蛇也會注意獵物的心跳——這說明這種行為是與生俱來的。這是可以解釋蟒蛇這種行為的很好的理由。作者稱，蟒蛇捕獵時的身體收縮會耗費大量的力氣。但這樣也很危險的，比如說，如果在蟒蛇盤繞在獵物身上的時候，天敵突然襲擊。但通過傾聽獵物心跳的方式，蟒蛇可以給獵物施加足夠的扼殺力，然后輕松享用美餐。
注：本文譯文屬可可英語原創，未經允許，請勿轉載。
