| 网站首页 | 文秘公文 | 免费试题 | 教学用文 | 优秀教案 | 各类考试 | 
您现在的位置: 东星资源网 >> 各类考试 >> 职称英语 >> 综合类 >> 正文
2008年职称英语考试阅读判断试题训练(十五)
2008年职称英语考试阅读判断试题训练(十五)

15A Dog’s Dilemma  狗的两难境地

Finding a babysitter while you go out to work is, for example, an inconvenience. For the African wild dog, one of the continent’s most endangered carnivores, it’s a matter of life and death. New research shows that once packs fall below a certain size, there are not enough animals to both hunt food and stay at home protecting the young.

The African wild dog has declined drastically over the past century. Habitual loss, persecution and unexplained outbreaks of disease have all been blamed. Only 3,000 to 5,000 animals remain, and the species is expected to go extinct within decades if the trend continues.

Other large carnivores such as the spotted hyena face similar pressures, yet are not declining. Now Franck Courchamp of Cambridge University has found a reason why. The dog’s weakness lies in its social organisation.

Within each pack of up to 20 adults and pups, only the dominant male and female breed. The remaining animals help raise the pups, cooperating to hunt prey and defend the kill from other carnivores.

Because pups can’t keep up on a hunt, large packs leave an adult behind to protect them from predators, which include lions and hyenas. But leaving a babysitter also carries costs. A smaller hunting party is less able to tackle large prey and to defend the kill. There is also one less stomach in which to carry food back to the den, and one more mouth to feed when they get there.

Courchamp investigated this awkward trade-off by modelling how the costs of a babysitter change with decreasing pack size. This showed that packs of more than five adults should be able to feed all the pups and still spare a babysitter. But with smaller packs, either the hunting or the babysitting suffers, or the animals have to compensate by increasing the number of hunting excursions - which itself carries a cost to the pack.

Field observations in Zimbabwe supported the model. Packs of five animals or fewer left pups unguarded more frequently than larger packs did. There was also evidence that when they did leave a babysitter, they were forced to hunt more often.

A pack which drops below a critical size becomes caught in a vicious circle, says Courchamp, who is now at Paris –Sud University. “Poor reproduction and low survival further reduces pack size, culminating in failure of the whole pack” And deaths caused by human activity, says Courchamp, may be what reduces pack numbers to below the sustainable threshold. Mammal ecologist Chris Carbone at London’s Institute of Zoology agrees. Maintaining the integrity of wild dog packs will be vital in preserving the species, he says.

例如,当你出去工作时找临时照顾孩子的保姆是不便。而大陆上最有灭绝危险的食肉动物非洲野狗来说,这是一件生死攸关的事情。新的显示一旦动物群低于某种规模,足够的动物既捕猎又留在家里保护幼儿。

世纪里,非洲野狗的急剧下降。原因是惯常的丧失、迫害和莫名其妙的疾病的爆发。只剩下3 000到5 000只野狗,势头下去的话,在数十年里,物种就会灭绝。

的大型食肉动物,如带斑点的袋狼也面临着类似的,但下降。现在,剑桥大学的富兰克·顾尚了原因。狗的弱点在于它的社会组织。在一群可以多达20只大小狗中,占支配地位的母狗和公狗可以产仔。的狗帮助养小狗,捕猎和防御食肉动物的捕杀。

小狗在猎食时跟不,大的狗群会留下一只成年的狗来保护它们而不受包括狮子、袋狼在内的捕食动物的伤害。留下一只看护狗要付出代价的。较小的捕猎群体不太容易捕捉大动物,也不太容易保卫猎获物。而且少了带食回窝的胃,回到窝还多了一张吃东西的嘴。

顾尚模拟狗群的减小看护狗的代价的两难境地。这显示多于五只成年狗的狗群应该能够喂养所小狗,并仍然能留一只狗做看护狗。规模稍小的狗群中,捕猎或看护小狗都会遭受损失,要么狗就得出猎的次数弥补——这本身就需要狗群付出代价。

在津巴布韦的野外观察支持模式。五只或五只的狗群比规模大些的狗群更经常地把小狗看护地独自留下。还有证据表明当它们留下一只看护狗时,它们不更经常地捕猎。

现在在巴黎大学的顾尚说,低于某特定规模的狗群会陷入恶性循环。“少量的繁殖和低存活率减小了狗群的规模,整个狗群的消亡。”顾尚说人类的死亡是使狗群低于可维持的最低点的原因。伦敦动物学所的哺乳动物生态学家克里斯·卡波恩也同意说法。他说非洲野狗群的完整对保护该物种是的。

★1).The African wild dog has been endangered.-R

★2).The spotted hyena is on the verge of extinction.-W

★3).The remaining lions will die out within decades.-N

★4).The dominant females is always left behind to protect the young.-W

★5).There is a tension between babysitting and hunting.-R

★6).The size of a pack must be big enough for it to survive.-R

★7).Steps will be taken to protect the African wild dog.-N

 

--下载<<2008年职称英语考试阅读判断试题训练(十五)>>Word文档 ,本文由东星资源网收集,版权归原作者所有
文章录入:admin    责任编辑:admin 
  • 上一个文章:

  • 下一个文章:
  • 发表评论】【加入收藏】【告诉好友】【打印此文】【关闭窗口
    相关综合类 最新热点 最新推荐
    名师指点:历年考研数学重点…
    迈入六月天 2010考研大纲出来…
    我的暑期我做主:2010考研数…
    2010年考研数学线性代数解题…
    专家指导:2010年考研数学命…
    2010年考研数学指导:掌握学…
    名师指点:搜索2010考研数学…
    六月备考:为你量身定制2010…
    2010年考研数学复习名师忠言…
    我的暑期我做主:成就2010年…
      各类考试导航:
    英语四六级考试试题   英语作文   技巧心得   复习指南
    公务员考试最新资讯   申论试题   行政职业能力   公务员面试试题   专业科目试题   公共科目试题   考试攻略   时事政治
    成人高考语文复习   英语复习   史地复习   理化复习   数学(文)   数学(理)   政治复习
    计算机等级考试最新动态   历年试题   政策说明   经验交流
    职称英语理工类   卫生类   综合类   经验交流
    商务英语
    护士执业考试临床护理   基础护理学   心理护理    中医护理
    考研资料工程硕士   MBA   法律硕士    在职研究生   同等学历   心得指南