英語聽力文摘 鬣狗的手足之爭

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A Hyena’s Sibling Rivalry

鬣狗，學(xué)名Hyaenidae，哺乳動(dòng)物，是體型中等、生活在非洲、阿拉伯半島、亞洲和印度次大陸的陸生肉食性動(dòng)物。它們同屬于一科：鬣狗科。外形略像狗，頭比狗的頭短而圓，毛棕黃色或棕褐色，有許多不規(guī)則的黑褐色斑點(diǎn)，食用獸類尸體腐爛的肉維生。

If you grew up with a brother or sister, you probably know what sibling rivalry is like. For a spotted hyena(黑斑鬣犬) though, sibling rivalry is a matter of life and death.

Spotted hyena mothers usually have twins. They give birth in a private burrow where the newborns live for the first few weeks of life. By the time the mother moves her offspring from the natalburrow to the community den however, there’s a fifty-fifty chance that one of her infants will be dead. What’s more, her children always emerge from their nursery covered with wounds.

A look inside the burrow reveals what’s going on. After a long gestation cycle, newborn hyenas are remarkably well developed. Like Red Riding Hood’s wolf, they have big, open eyes and full sets of(一整套) teeth. They won’t hunt for many months to come, so what are these adaptations for?

Hyena infants fight each other from the moment they’re born, and often begin their struggles inside the amniotic sac(羊膜囊). Same sex newborns fight to the death, while brother-sister struggles usually leave both cubsbattered but alive.

You might wonder why this behavior evolved in the first place? What possible advantage could there be in killing off your closest relative?

The answer might have to do with adult hyena table manners(飯桌禮儀). Hyenas hunt together, but once they’ve brought down their prey it’s every hyena for itself in a violent feeding frenzy, where the most vicious hyenas steal away the most food.Fighting to the death at its mother’s teats might give an infant hyena some good practice for this adult behavior.