Review of Wolves and the Ecology of Fear: Can Predation Risk Structure Ecosystems?

In this article, authors William Ripple and Robert Beschta focus on the issue of predation and the way it affects biodiversity and otherwise alters ecosystems. While many other studies have stressed the lethal effects of predation by carnivores, the authors of this study have chosen to focus on how nonlethal outcomes of predation affect the structure and function of ecosystems. The authors give two main objectives to their study: first to provide a short synthesis of the potential ecosystem responses to predation risk in a three-level trophic cascade involving large carnivores, hoofed animals, and vegetation; and secondly to present research that centers on wolves, elk, and woody browse species in the northern area of Yellowstone National Park.

The authors begin by defining several terms in depth. First, the term trophic cascade is defined in the context of the study. In this study, the authors focus on top-down processes and the ways in which related trophic interactions could have effects on ecosystems. They also discuss ways in which predators can influence the size of prey species populations in large and small scales. Additionally, the nonlethal effect of changes in prey behavior are discussed; this can include changes in herbivores’ use of spaces such as foraging patters within a habitat or even habitat preference. These changes are caused by fear of predation. Next, prey and plant refugia are discussed. Prey refugia are areas occupied by prey where they are less likely to encounter a predator. In the status quo, predation risks may occur due to human hunting. A previous study found that in St. John, Montana, elk adjusted their eating behaviors by browsing far from roads in order to avoid human contact. The authors ...

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...k can in fact structure ecosystems. Based on their theories regarding trophic cascades and predation risks as well as other research conducted on similar issues, the authors determined that predation risk affects ecosystems in both subtle and dramatic ways through many interactions, some of which remain unknown.

Ultimately, the authors believe that based on their findings, the future of management of the northern range ungulate herds must focus on the recovery of natural processes. They also believe that in addition to restoring large carnivores such as wolves, it is also important to recover historic hoofed migrations. The authors finally concede to the fact that because their research focused solely on the northern range of Yellowstone National Park, it would be difficult to make conclusions about other areas in North America where wolves have been extirpated.