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OFFICIAL38 According to paragraph 4, how has the spread of agriculture affected raccoon populations?

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The Raccoons's Success
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Raccoons have a vast transcontinental distribution, occurring throughout most of North America and Central America. They are found from southern Canada all the way to Panama, as well as on islands near coastal areas. They occur in each of the 49 states of the continental United States. Although raccoons are native only to the Western Hemisphere, they have been successfully transplanted to other parts of the globe.

Following a decline to a relatively low population level in the 1930s, raccoons began to prosper following their 1943 breeding season. A rapid population surge continued throughout the 1940s, and high numbers have been sustained ever since. By the late 1980s, the number of raccoons in North America was estimated to be at least 15 to 20 times the number that existed during the 1930s. By now, their numbers have undoubtedly grown even more, as they have continued to expand into new habitats where they were once either rare or absent, such as sandy prairies, deserts, coastal marshes, and mountains. Their spread throughout the Rocky Mountain West is indicative of the fast pace at which they can exploit new environments. Despite significant numbers being harvested and having suffered occasional declines, typically because of disease, the raccoon has consistently maintained high population levels.

Several factors explain the raccoon's dramatic increase in abundance and distribution. First, their success has been partially attributed to the growth of cities, as they often thrive in suburban and even urban settings. Furthermore, they have been deliberately introduced throughout the continent. Within the United States, they are commonly taken from one area to another, both legally and illegally, to restock hunting areas and, presumably, because people simply want them to be part of their local fauna. Their appearance and subsequent flourishing in Utah's Great Salt Lake valley within the last 40 years appears to be from such an introduction. As an example of the ease with which transplanted individuals can succeed, raccoons from Indiana (midwestern United States) have reportedly been able to flourish on islands off the coast of Alaska.

The raccoon's expansion in various areas may also be due to the spread of agriculture. Raccoons have been able to exploit crops, especially corn but also cereal grains, which have become dependable food sources for them. The expansion of agriculture, however, does not necessarily lead to rapid increases in their abundance. Farming in Kansas and eastern Colorado (central and western United States) proceeded rapidly in the 1870s and 1880s, but this was about 50 years before raccoons started to spread out from their major habitat, the wooded river bottomlands. They have also expanded into many areas lacking any agriculture other than grazing and into places without forests or permanent streams.

Prior to Europeans settling and farming the Great Plains Region, raccoons probably were just found along its rivers and streams and in the wooded areas of its southeastern section. With the possible exception of the southern part of the province of Manitoba, their absence was notable throughout Canada. They first became more widely distributed in the southern part of Manitoba, and by the 1940s were abundant throughout its southeastern portion. In the 1950s their population swelled in Canada. The control of coyotes in the prairie region in the 1950s may have been a factor in raccoon expansion. If their numbers are sufficient coyotes might be able to suppress raccoon populations (though little direct evidence supports this notion). By the 1960s the raccoon had become a major predator of the canvasback ducks nesting in southwestern Manitoba.

The extermination of the wolf from most of the contiguous United States may have been a critical factor in the raccoon's expansion and numerical increase. In the eighteenth century, when the wolfs range included almost all of North America, raccoons apparently were abundant only in the deciduous forests of the East, Gulf Coast, and Great Lakes regions, though they also extended into the wooded bottomlands of the Midwest's major rivers. In such areas, their arboreal habits and the presence of hollow den trees should have offered some protection from wolves and other large predators. Even though raccoons may not have been a significant part of their diet, wolves surely would have tried to prey on those exposed in relatively treeless areas.

8.According to paragraph 4, how has the spread of agriculture affected raccoon populations?

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正确答案:C
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【题目翻译】根据第4段,农业的蔓延对浣熊种群有何影响? A:农业的蔓延破坏了浣熊的一些自然栖息地,并减少了它们在堪萨斯州和科罗拉多州东部的数量。 B:由于农业的普及,玉米和其他谷类作物的供应量大。 C:农业的普及可能导致了一些浣熊的扩张,但并不总是导致浣熊种群的扩张。 D:在19世纪70年代和19世纪80年代,堪萨斯州和科罗拉多州东部的农业扩张带来了浣熊数量的增加。 【判定题型】:题目问的是文章中的具体细节信息,故根据题目问法可以判断本题为事实信息题。 【关键词定位】本题根据题干中的关键词the spread of agriculture定位到这两句:The raccoon's expansion in various areas may also be due to the spread of agriculture. 和 The expansion of agriculture, however, does not necessarily lead to rapid increases in their abundance. 意思是“农业的扩张也可能是浣熊扩张的原因之一,但是农业的扩张并不一定会导致浣熊数量的迅速增长”。 【逻辑分析】:结合题目问法和出题句,进行逻辑分析。 【选项分析】 A.未提及农业的扩张和浣熊数量减少的关系,故错误。 B.未提及农作物的供应量,故错误。 C.符合文意,正确。 D.文中“但是直到50年后浣熊才从主要栖息地—长满树木的河流低地—开始向外扩张”,选项歪曲了文章的意思,故错误。

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