Department of Biological Sciences, Mississippi State University, Mississippi State, Mississippi, 39762, USA.
Department of Wildlife, Fisheries, and Aquaculture, Mississippi State University, Mississippi State, Mississippi, 39762, USA.
Ecology. 2018 Jul;99(7):1517-1522. doi: 10.1002/ecy.2365. Epub 2018 Jun 6.
Giving-up density (GUD) experiments have been a foundational method to evaluate perceived predation risk, but rely on the assumption that food preferences are absolute, so that areas with higher GUDs can be interpreted as having higher risk. However, nutritional preferences are context dependent and can change with risk. We used spiders and grasshoppers to test the hypothesis that covariance in nutritional preferences and risk may confound the interpretation of GUD experiments. We presented grasshoppers with carbohydrate-rich and protein-rich diets, in the presence and absence of spider predators. Predators reduced grasshopper preference for the protein-rich food, but increased their preference for the carbohydrate-rich food. We then measured GUDs with both food types under different levels of risk (spider density, 0-5). As expected, GUDs increased with spider density indicating increasing risk, but only when using protein-rich food. With carbohydrate-rich food, GUD was independent of predation risk. Our results demonstrate that predation risk and nutritional preferences covary and can confound interpretation of GUD experiments.
放弃密度（GUD）实验一直是评估感知捕食风险的基础方法，但它依赖于这样一个假设，即食物偏好是绝对的，因此 GUD 较高的区域可以被解释为具有更高的风险。然而，营养偏好是依赖于环境的，并且可能随着风险的变化而变化。我们使用蜘蛛和蚱蜢来测试以下假设：营养偏好和风险之间的协方差可能会混淆 GUD 实验的解释。我们在有和没有蜘蛛捕食者的情况下，为蚱蜢提供富含碳水化合物和蛋白质的食物。捕食者降低了蚱蜢对富含蛋白质食物的偏好，但增加了它们对富含碳水化合物食物的偏好。然后，我们在不同风险水平（蜘蛛密度，0-5）下使用这两种食物类型测量 GUD。正如预期的那样，GUD 随着蜘蛛密度的增加而增加，表明风险增加，但仅在使用富含蛋白质的食物时才会出现这种情况。对于富含碳水化合物的食物，GUD 与捕食风险无关。我们的结果表明，捕食风险和营养偏好是相互关联的，可能会混淆 GUD 实验的解释。
