考古： byhelio`（680）专家们研究觅食行为，觉得跟predator有关，那个动物，下面用A代替好了，专家们觉得如果A预测捕食者很多，就会怎么怎么样，好像是说吃更少。但是实际上，它们是减少了觅食点的数量，or缩短了各个觅食点之前的距离，or加快了在各个觅食点行动的速度（因为文章后面和题目里有考到这些点，现在回忆都是混的，大家看的时候仔细点），然后在各个觅食点吃很多，从而不会减少吃的东西的总量。 第二段讲专家研究觅食行为和prediction of predators的关系。好像从两方面考虑，如果多会怎样，如果少会怎样，具体也忘了。。也有提到population density。不过好像都是他们的猜测。 第三段是讲专家给一些A设了栅栏，研究它们的觅食行为。他们猜测在栅栏外面的A的觅食行为在预测捕食者比较多的情况下，应该会怎么样，而栅栏里面的会怎么样，但是没想到栅栏里面的与栅栏外面的行为是一样的，并没有因为受fence的影响。这其中的行为有讲到找cover啊，缩短觅食点的距离等等。后来又观察到什么现象，于是发现A的觅食行为可能不是跟对捕食者的预测有关而是跟其他一个因素有关，好像是对食物的preference？？忘了。。 有assumption题，印象中定位在第一段最后几句 有主旨题
bymikiluang应该是说它们的一种迁徙，一开始的科学家认为他们的move的distance是depend on food
by zzzlll012345（670）第三篇阅读貌似是说snowshoe hare的，真他NND长啊这篇。。。说科学家刚研究snowshoe fare 的forage行为的影响因素，researchers发现某处fare被捕食的几率在近几年大大减少，其原因是因为fare本身的density变少，而捕食者的数量则基本没变（我觉得我这里要不是记错了就是理解错了。。大家见谅，反正大概就是这个意思，到时候考场的时候注意看一下就OK）先假设其行为是因其对捕食者的预期而改变，而fare对于捕食者风险的判断标准不同分为两种情况，第一种是在fare被追逐的时候fare认为他们被捕食，另一种是在fare发现捕食者踪迹的时候就断定他们有被捕食的危险，于是这两种不同标准的判断导致了其forage行为被影响的程度。。然后捕食者又在一处地方设立了栅栏，在建立栅栏的区域内没有捕食动物，并且观察在栅栏内的fare和栅栏外的fare的forage的行为并没有差别，于是researcher假设fare的影响forage的因素并不是被捕食的预期而可能是preference。 PS这篇的考点很细，感觉蛮恶心的，大家考试的时候仔细点。。
by lyincat(720M51V36)题目有：问在大部分实验中，s,l,c的数量有什么变化。我选的他们的数量维持constant(因为研究者最后说s收到的威胁没变)。还有问以下那个说法正确，我选的s在很多情况下可以从l,c手中逃走。最后一题问的哪个最能削弱最后一段的结论，我选的s藏在篱笆下的地方有很多小洞，他们可以快速从那里逃走但l,c却过不了那个洞。
bywalter1987 (730)snowshoe hare foraging behavior的那个题，的确巨长，一屏半，机经的结构还是差不多的，其中第二段没有题，可以看得快一点，第三段比较重要，说的是兔子被用篱笆关起来以后，这样可以避免天敌的存在，但是发现兔子的捕食行为没有改变，由此得出结论说兔子的捕食行为跟天敌没有关系，主要是跟食物的可得性有关。
I examined the effects of predation risk on the behaviour and population dynamics of snowshoe hares (Lepus americanus) during a cyclic peak and decline (1989-1993) near Kluane Lake, Yukon. Like most heavily preyed upon animals, snowshoe hares have to balance conflicting demands of obtaining food at a high rate and avoiding predators. The consequences of adopting predator avoidance behaviours under high risk of predation in winter may influence population dynamics of hares.
Changes in patterns of winter habitat use, survival, body mass, and female reproduction were compared on four experimental areas: (i) where predation risk was reduced by excluding-out terrestrial predators (FENCE), (ii) where food supply was supplemented with ad lib rabbit chow (FOOD), (iii) a combination of these two treatments (FENCE+FOOD), and (iv) an unmanipulated CONTROL. Three hypotheses were compared. The food hypothesis predicts that hares use habitats with the highest amounts of food: body mass remains high, but survival is reduced. The predator avoidance hypothesis predicts that hares use habitats with the lowest risk: survival is high, but body mass decreases. The predation-sensitive foraging (PSF) hypothesis predicts that both survival and body mass decline because a trade-off exists between predation risk and food availability. At peak densities hares used open habitats where food was readily available. However, as predation risk increased during the population decline, hares increased their use of safer, closed habitat and shifted their diet to include a greater proportion of poorer quality spruce twigs. This change in behaviour resulted in lower female body mass and reduced fecundity on the CONTROL area, even though sufficient winter forage was available. A similar decrease in body mass was observed on the FOOD treatment during the third year of the population decline. On FENCE+FOOD, female body mass and fecundity remained high during the decline. Similarly, body mass did not decline on the FENCE treatment. These results supported the PSF hypothesis where terrestrial predators were present (CONTROL and FOOD), and the food hypothesis where terrestrial predators were absent (FENCE and FENCE+FOOD). Hares appear to have a limited ability to reduce exposure to predators because they have no absolutely safe refuge from predators, and they have limited reserves of energy during winter. Preliminary evidence suggests that physiological stress associated with high risk and poor condition is elevated during the population decline. I suggest that deleterious maternal effects mediated by predation risk may introduce a lag of one generation into the 10- year population cycle of snowshoe hares.
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发表于 2011-10-5 12:16:22
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