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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.
In Swedish researchers’ opinion, poaching has caused
选项 A、a serious damage of GPS tracking function.
B、a potential threat to wolves’ thriving.
C、the direct invention of a mathematical analysis.
D、a sharp decrease in the number of wolves.
答案B
解析 推理判断题。由题干关键词Swedish researchers’s opinion和poaching定位到第一段。该段介绍瑞典狼的数量因偷猎而减少，最后一句指出科学家估算因偷猎致死的狼占斯堪的纳维亚狼群死亡数量的一半，对这种珍稀食肉动物的数量恢复造成了潜在的阻碍。由此可推断，偷猎对狼群的兴旺繁衍造成了潜在的危险。[B]的意思与之一致，故为答案。文中虽然提到狼神秘失踪而且套在它们脖子上的GPS项圈信号突然中断，研究者们怀疑这是偷猎造成的，但这并非本文讨论的重点，文章讨论的重点是偷猎与狼数量减少之间的因果关系，故排除[A]；而[D]中的sharp与原文中的potential不符，故排除。
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