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  3. Wolves have been disappearing mysteriously in Sweden. Between 1999 and 2009, 18 of the animals—or about 17% of the individuals t

Wolves have been disappearing mysteriously in Sweden. Between 1999 and 2009, 18 of the animals—or about 17% of the individuals t

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问题     Wolves have been disappearing mysteriously in Sweden. Between 1999 and 2009, 18 of the animals—or about 17% of the individuals that researchers have actively followed—have gone missing; the global positioning system(GPS)collars used to track them suddenly blinked off, and the wolves never reemerged. Researchers suspected poaching, but it’s been hard to determine how much of a toll such clandestine kills have taken. Now, by using a new mathematical analysis, scientists have estimated that poaching accounts for half the deaths of Scandinavian wolves, potentially stymieing the rare predator’s recovery.
    As recently as the 1970s, not a single wolf lived in Norway or Sweden, says Guillaume Cha-pron, a conservation scientist at the Swedish University of Agricultural Sciences in Riddarhyttan and a co-author of the new study. DNA evidence has shown that those carnivores living in the region today descend from a single male-female pair that made the treacherous trek from Finland in the early 1980s and a second male that arrived in 1991. Packs have grown steadily from those three founders; in 2009, Sweden and Norway were home to 263 wolves.
    To keep an eye on their numbers, Scandinavian researchers fitted 104 wolves with GPS collars between 1999 and 2009. When a GPS blip goes dead, conservationists with the Scandinavian Wolf Project SKANDULV go looking. Some teams circle wolf territories in helicopters, whereas others set out on skis or snowmobiles to follow tracks and locate scat for DNA testing. If these extensive searches turn up nothing, as happened with 18 wolves that disappeared over the past 10 years, Chapron and his colleagues suspect foul play. "We cannot find any other mortality cause that would destroy the wolf and the radio-tracking collar other than poaching," he says.
    But bodies still haven’t turned up for any of the lost wolves. Chapron suspects that poachers disposed of their remains and the GPS collars to cover up the crimes. So instead, the researchers turned to ecology to show the extent of poaching in Scandinavia. Chapron and his colleagues projected how fast the Scandinavian wolf packs should have grown between 1999 and 2009. Had wolves died only from known causes—illnesses, speeding cars, and a few cases of confirmed poaching—numbers would have grown from 74 animals to nearly 700. But in 2009, researchers counted fewer than 300 wolves in Sweden and Norway.
    Poachers didn’t kill 400 wolves directly but took out an unknown number of males and females that would’ve otherwise been able to breed and multiply. "You cannot really explain the population counts," Chapron says. "You need an extra source of mortality. " In other words, hidden poaching.
    Regardless of the motive, illegal kills account for about 50% of total wolf deaths in Scandinavia, Chapron and colleagues estimate. In two-thirds of those cases, poachers seem to be killing and ditching the evidence without anyone knowing. Such "cryptic poaching" takes a whopping toll on the population, and it’s one that has gone unrecognized until now.
When did the first group of wolves in Norway and Sweden come into being?
选项 A、In the early 1970s.
B、In the early 1980s.
C、In the early 1990s.
D、In the early 21st century.
答案C
解析 推理判断题。根据题干中first group和Norway and Sweden定位到第二段最后两句。这两句介绍了挪威和瑞典地区狼群繁衍发展的情况，指出DNA证据表明目前生活在该地区的狼群的祖先，分别是20世纪80年代早期从芬兰长途跋涉过来的一对公狼母狼以及1991年迁移至此的一只公狼。在这三只狼的基础上，本地狼的数量稳步增长。由此可知，第一个狼群应为该段提到的那三只狼，根据第三只狼来此地的年代1991年可判断，这个群落构成的时间是20世纪90年代早期。故[C]与原文相符，是正确答案。
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