Fairweather P G, Underwood A J
School of Biological Sciences, University of Sydney, Zoology Building, 2006, N.S.W., Australia.
Oecologia. 1983 Feb;56(2-3):169-179. doi: 10.1007/BF00379688.
In order to estimate the true diet of predators, the prey of a number of predators is recorded at one time. Such sampling underestimates the true diet during a period of time. Where handling times of different types of prey are very different, these estimates will be biased, because prey that take a relatively long time to be eaten will be overestimated. We examined a rocky intertidal predatorprey system and demonstrated the existence of such bias. A number of hypothetical correlates of the bias were also investigated. As anticipated, variations in handling times were a major factor, but neither taxonomic affinity nor absolute size of the prey could predict the degree of underestimation in the true diet for any given type of prey. A previously described correction for this type of bias was tested, but found to be unsatisfactory. We suggest that it was too insensitive to variability in handling times.A simple computer model incorporating differences among prey in their handling times was also unable to predict the bias, but did indicate that non-random selection of prey was occurring.We concluded that where such biases are likely to occur, information on the handling times of different prey and/or accurate estimates of the true diets of the predators are essential for the predatory interaction to be interpreted properly. These results were discussed in relation to published accounts of diets of predators in rocky intertidal habitats. Many studies have not presented data on handling times of prey in the field, and the magnitude and importance of potential biases in these studies are therefore difficult to assess.
为了估计捕食者的真实食谱，一次记录了许多捕食者的猎物。这样的抽样低估了一段时间内的真实食谱。当不同类型猎物的处理时间差异很大时，这些估计会有偏差，因为食用时间相对较长的猎物会被高估。我们研究了一个岩石潮间带捕食者 - 猎物系统，并证明了这种偏差的存在。还研究了一些与该偏差相关的假设因素。正如预期的那样，处理时间的变化是一个主要因素，但猎物的分类学亲缘关系或绝对大小都无法预测任何给定类型猎物在真实食谱中的低估程度。对先前描述的针对这种偏差的校正方法进行了测试，但发现并不令人满意。我们认为它对处理时间的变异性过于不敏感。一个纳入猎物处理时间差异的简单计算机模型也无法预测这种偏差，但确实表明存在对猎物的非随机选择。我们得出结论，在可能出现这种偏差的情况下，关于不同猎物处理时间的信息和/或对捕食者真实食谱的准确估计对于正确解释捕食相互作用至关重要。结合已发表的关于岩石潮间带栖息地捕食者食谱的记录对这些结果进行了讨论。许多研究没有给出野外猎物处理时间的数据，因此很难评估这些研究中潜在偏差的程度和重要性。
