Collaborative Research: Does Anti-predator Behavior Modify Indirect Effects of Top Predators?

捕食者可以通过吓跑食草动物和防止过度放牧来使植物受益，这一过程被称为“营养瀑布”。生物学家假设，每一种捕食者都会创造一种营养级联。例如，一只老虎可以吓跑食草动物，并保护它巡逻地区的植物。然而，证据表明，并不是所有的食草动物都对捕食者的恐惧做出一致的反应。相反，在有多个草食动物的生态系统中，每一种草食动物都可能避开最不可能逃脱捕食者的区域，这些区域可能会有所不同。如果是这样，那么捕食者可能会触发一系列营养级联，使任何特定草食动物最有可能被捕获的植物受益。为了了解捕食者如何通过吓跑食草动物来保护植物，生物学家必须确定每个猎物物种最不可能逃脱的区域或栖息地类型。这样的识别需要了解猎物逃跑的战术。这项拟议的研究将使用华盛顿两种食草动物--骡子和白尾鹿--的逃跑策略来预测灰狼最近的回归对它们栖息地使用的变化。骡鹿速度很慢，用它们的敏捷来躲避捕食者。他们将被期望转移到他们的敏捷性有利的崎岖地形，并避免平坦的地形，那里的逃生需要速度。白尾鹿速度很快，会通过冲刺逃脱捕食者；当受到狼的惊吓时，它们应该会避开崎岖的地形，因为那里它们的速度是中性的。因此，狼应该保护生长在平缓地形上的骡鹿所吃的植物，以及生长在崎岖地形上的白尾鹿所吃的植物。该项目将通过强调猎物逃逸行为在驱使捕食者影响植物和塑造生态系统方面的重要性，改变人们对捕食者生态作用的理解方式。研究的更广泛影响包括培训两名博士生，建立一项关于狼的生态影响的长期研究，作为一种为保护政策提供信息的手段，以及启动一个包括教师培训、公共讲座和中学课堂视频课程计划的推广计划。

Predators can benefit plants by scaring away herbivores and preventing overgrazing in a process known as a "trophic cascade." Biologists have assumed that each predator creates one kind of trophic cascade. A tiger, for example, scares herbivores away from and protects plants growing in the area it patrols. Evidence suggests, however, that not all herbivores respond uniformly to the fear of predators. Instead, in ecosystems with multiple herbivores, each one may avoid the area where it is least likely to escape the predator, and these areas might differ. If so, then predators could trigger an array of trophic cascades, benefiting plants eaten by any particular herbivore where it is most likely to be caught. To understand how a predator shields plants by scaring away herbivores, biologists must identify the area, or habitat type, where each prey species is least likely to escape. Such identification requires knowledge of prey escape tactics. The proposed research will use escape tactics of two herbivores in Washington -- mule and white-tailed deer -- to predict changes to their habitat use caused by the recent return of the gray wolf. Mule deer are slow, and use their agility to escape predators. They would be expected to shift to rough terrain where their agility is advantageous, and avoid smooth terrain where escape requires speed. White-tailed deer are fast and escape predators by sprinting away; when frightened by wolves they would be expected to avoid rugged terrain where their speed is neutralized. Consequently, wolves would be expected to protect plants eaten by mule deer that grow on gentle terrain, and plants eaten by white-tailed deer that grow on rugged terrain. This project will change the way that the ecological role of predators is understood, by highlighting the importance of prey escape behavior in driving how predators affect plants and shape ecosystems.The broader impacts of the research include training of two doctoral students, establishment of a long-term study of the ecological impacts of wolves as a means to inform conservation policy, and initiation of an outreach program incorporating teacher training, public lectures, and video lesson plans for secondary school classrooms.