Most people think of zoos as safe places for animals, where struggles such as difficulty finding food and avoiding predators (猛兽) don't exist. Without such problems, animals in zoos should live to a ripe (成熟的) old age1.
But that may not be true for 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 (圈养) 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 of thousands of female wild elephants in Africa and Asian elephants that work in logging camps(伐木场),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 lived 41.7 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 (肥胖症) may be to blame. 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.
The study raises some questions about acquiring more elephants to keep in zoos. While some threatened and endangered species living in zoos reproduce (生殖) successfully and maintain healthy populations, that doesn't appear to be the case with elephants.
41 Unlike other animals in zoos, zoo-raised elephants
A live a long life
B give birth to many babies
C develop poor health
D have difficulty getting food
42 Which of the following about the international scientists' study is NOT true?
A They compared zoo elephants with wild elephants.
B They analyzed the records of the elephants kept in zoos.
C The zoo-born elephants they studied are kept in European zoos.
D They kept detailed records of all the elephants in their care.
43 It was found that, compared with female wild elephants, female zoo-born elephants
A lived longer.
B grew up faster.
C died much earlier.
D enjoyed the same life spans.
44 One of the possible reasons for the Zoo-raised elephants' problems is that
A they do not get enough exercise.
B they do too much exercise.
C they live in large herds.
D they do not live in family groups.
45 It can be inferred from the last paragraph that
A Zoo-born elephants should be looked after more carefully.
B Zoos should keep more animals except elephants.
C It may not be a wise policy to keep elephants in the zoo.
D Elephants are no longer an endangered species.
参考答案:41 C 42 D 43 C 44 D45 C
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