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  3. The cycle of fluctuation in snowshoe hare populations is unusual among anima

The cycle of fluctuation in snowshoe hare populations is unusual among anima

游客2025-02-19  8
问题     The cycle of fluctuation in snowshoe hare populations is unusual among animal species in that it is remarkably regular—peaking every eight to eleven years—and broadly synchronized over a vast area. Declines from peak levels are initiated by markedly lower overwinter survival of young hares, sharp decreases in birth rates, and a declining survival rate for adult hares. The onset of population increases is brought about by greatly improved rates of survival and birth.
    Some biologists hypothesize that the cycle begins when peak snowshoe hare populations exceed their winter food supply; resulting malnutrition triggers a population decline. As hare numbers fall, the ratio of predators to hares increases, as does the impact of predation on the hare population. This extends the decline beyond the period of winter food shortage. Hare scarcity then causes predator population declines, and with fewer predators and more abundant winter food, the hare population begins another cyclic increase. The high mobility of predators responding to local differences in hare abundance contributes to interregional synchrony. [br] The passage suggests that population fluctuations in many other animal species differ from those of the snowshoe hare in that population fluctuations in other species
选项 A、are less regular due to more erratic changes in predator levels
B、typically occur over a longer time period
C、are synchronized over larger areas
D、are less dependent on food availability
E、are typically less predictable
答案 E
解析 根据第一段第一句可知，北美野兔和其他物种之间的区别在于北美野兔的种群波动更加规律因而可以预测，因此选项E正确。
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