Most people think of zoos as safe places for animals，where struggles such as difficulty finding food and avoiding predators don’t exist. Without such problems，animals in zoos should live to a ripe old age1.
But that may not be true for2 the largest land animals on Earth. Scientists have known that elephants in zoos often suffer from poor health. They develop diseases，joint problems and behavior changes. Sometimes, they even become infertile，or unable to have babies.
To learn more about how captivity affects elephants，a team of international scientists compared the life spans of female elephants born in zoos with female elephants living outdoors in their native lands. Zoos keep detailed records of all the animals in their care，documenting factors such as birth dates, illnesses, weight and death. These records made it possible for me researchers to analyze 40 years of data on 800 African and Asian elephants in zoos across Europe. The scientists compared the life spans of the zoo-born elephants with the life spans 癫痫病能治好么of thousands of female wild elephants in Africa and Asian elephants that work in logging camps3，over approximately the same time period.
The team found that female African elephants born in zoos lived an average of 16.9 years. Their wild counterparts who died of natural causes lived an average of 56 years-more than three times as long. Female Asian elephants followed a similar pattern. In zoos，they lived 18.9 years，while those in the logging camps lived41.7 years.
Scientists don't yet know why wild elephants seem to fare so much better than their zoo-raised counterparts. Georgia Mason，a biologist at the University of Guelph in Canada who led the study，thinks stress and obesity may be to blame4.Zoo elephants don't get the same kind of exercise they would in the wild，and most are very fat. Elephant social lives are also much different in zoos than in the wild，where they live in large herds and family groups.
Another finding from the study showed that Asian elephants born in zoos were more likely to die early than Asian elephants captured in the wild and 全国好的癫痫病医院brought to zoos. Mason suggests stress in the mothers in zoos might cause them to have babies that are less likely to survive.
The study raises some questions about acquiring more elephants to keep in zoos. While some threatened and endangered species living in zoos reproduce successfully and maintain healthy populations，that doesn't appear to be the case with elephants. "Currently，zoos are net consumers of elephants，not net producers," Mason says.
predator n.食肉动物 captivity/ n.监禁;束缚
ripe adj.成熟的 fare v.过活，生活
infertile adj.不生育的 obesity n.过度肥胖;肥胖症
1.1ive to a ripe old age：这是一种固定用法，意思是live to an age that is considered to be very
2.be true for：或者be true of：对……适用。短文中第二段第一句：But that may not be true for
the largest land animals on Earth.这里，作为主语的that指的是第一段所陈述的内容。这个句子要传达的意思是：动物园对其他动物来说是一个安栖之地，而对大象来说却不然。
4.stress and obesity may be to blame：压力和肥胖是问题的根源。be to blame：该受责备，应承担责任。
1.According to癫痫病怎么治好 the first two paragraphs，unlike other zoo animals，zoo elephants
A.have difficulty eating food.
B.1ive to a ripe old age.
C.are not afraid of predators.
D.develop health problems.
2.Which of the following about the international scientists' research on the life spans of elephants is NOT true?(See paragraph 3)?
A.They compared zoo elephants with wild elephants.
B.They kept detailed records of all the elephants in their care.
C.They analyzed the records of the elephants kept in zoos.
D.The zoo-born elephants they studied are kept in European zoos.
3.What do the scientist find in their research?
A.Female elephants live longer than male elephants.
B.Female zoo elephants live longer than their wild counterparts.
C.Female zoo elephants die much earlier than their wild counterparts.
D.Elephants in zoos and those in the wild enjoy the same long life spans.
4.What are the possible causes of stress and obesity Zoo-raised elephants generally suf癫痫病如何治疗才正确fer from?
A.They do not like living in herds.
B.They do not get enough exercise.
C.They do not live with their families.
D.Both B and C.
5.Which of the following does the author suggest in the last paragraph 7?
A.It may not be a wise policy to keep elephants in the zoo.
B. Elephants are no longer an endangered species.
C.Zoo-born elephants should be looked after more carefully.
D.Zoos should keep more animals except elephants.
4.D 短文的第五段提供了答案。该段第三句的意思是：动物园里的大象不像野生大象那样活动，因此非常肥胖。他们也不像野生大象那样过着群居的生活，即live in herds and family groups。