英语听力:自然百科 野性俄罗斯之西伯利亚 Siberia—4(在线收听

 Even though the deer have a poor sense of smell, the musk manages to attract mates. Unfortunately, the human trade in musk glands has reduced the deer's numbers dramatically. And because only two thirds of the females have

 
fawns each year, the population replenishes slowly. After feeding, they chew the cud, regurgitating their meal and chewing it again to help digesting. They are relaxed. He keeps alert. 
 
In a nearby clearing, ravens benefit from the death of one of the pregnant horses. Their sharp beaks can strip clean the picked-over carcass. The group name for ravens is "unkindness", and they are both fierce and intelligent. They can make over 30 different kinds of sounds. But howling wolves frighten even them. 
 
Wolves don't hibernate, so they are constantly on the prowl for food. In autumn and winter, packs become nomadic, moving from place to place in search of a meal. Guided by their sharp sense of smell, they'll hunt, steal or scavenge whatever it takes to fill their bellies. The hungry wolves attack the meat with such ferocity that they even intimidate each other. 
 
For the birds, it's time for some fun. Like mammals, birds love to play. And the ravens are some of the silliest
  原文地址:http://www.tingroom.com/lesson/zrbaike/2011/259562.html