Wednesday, 22 May 2019

The Ecological Role of Wolves

The Ecological Role of Wolves

“The World of Wolves”

Edited by Marco Musiani, Luigi Boitani and Paul C. Paquet

The Ecological Role of Wolves 

Predation is an intensively studied phenomenon in ecology, and the body of knowledge on wolves and prey is significant. Wolf and ungulate ecology and behaviour provide an easily accessible gateway through which to understand predator-prey relationships. Accordingly, this book provides some responses to a fundamental and pragmatic question posed by Mark Boyce (2005). Specifically, what has this incredible catalogue of research on wolves done to enhance our understanding of the biology and ecology of predation?

The Ecological Role of Wolves - photo 1

The Ecological Role of Wolves

The Ecological Role of Wolves. Hebblewhite and Smith examine the role of wolves in ‘trophic cascades,’ ecosystem effects in which the consumer-resource relationship (e.g., wolves vs. elk) alters the abundance, biomass or productivity of population community or trophic level across more than one link in a food web (e.g., forage). The authors found evidence for direct effects as well as for trophic cascades triggered by wolves in Yellowstone and Banff National Parks. Direct effects in both systems included limitation or regulation of elk populations by wolves, behavioural avoidance of wolves by elk, and competition (both exploitative and interference) with other large carnivores.

The Ecological Role of Wolves - photo 2

The Ecological Role of Wolves

The Ecological Role of Wolves. Evidence for trophic cascade effects in the elk/wolf system include its influence on willow and aspen growth, and subsequently on species that rely on these plants, including beavers and a number of riparian songbirds. Furthermore, a trophic cascade effect may also explain apparent competition between elk and alternate prey, such as bison, moose, and caribou, that are mediated by wolf predation. A book is the ideal medium with which to provide results for longterm studies, in combination with summaries and syntheses of findings. Vucetich et al. (this volume) consider the relationship of wolves and moose in the world’s most intensely studied wolf and prey system, Isle Royale. 

The Ecological Role of Wolves - photo 3

The Ecological Role of Wolves

The Ecological Role of Wolves. The chapter demonstrates how after 50 years of observation by academics, each five-year period of the wolf-moose chronology seems decisively different from every other five-year period. The significance of this chapter is that lessons from such a dynamic system are frequently presented in articles, and most ecology textbooks, as static dogmas, therefore informing management in ways that vary every five years. Vucetich et al. also show that journal articles have seem to have primarily focused on the relationships between wolf and prey, on modeling those relationships, and then predicting future trends.

The Ecological Role of Wolves - photo 4

The Ecological Role of Wolves

The Ecological Role of Wolves. The authors provocatively conclude that, in fact, ecological explanations entailing predictive ability were not found. On the other hand, various studies provided ecological explanations entailing accurate, but non-predictive explanations of the past. Finally, by studying wolf and prey relationships, researchers have learned about new mechanisms regarding predation and its ecosystem effects. For example, unexpected mechanisms were reported linking wolves, moose, scavengers, and vegetation, and some fundamental effects of climate and disease on these mechanisms were also uncovered. 

The Ecological Role of Wolves - photo 5

The Ecological Role of Wolves

The Ecological Role of Wolves. Although clearly avoiding scholarly discussions, this book is at the core of current enquiries concerning bottom-up and top-down effects on ecosystems. As an apex predator, the wolf is often defined at the top of ecological pyramids. Vucetich et al. underscore the intellectual effort that is being invested into assessing whether, and if so, how, wolves affect the densities of herbivores. As shown by Creel and Christianson (2008), it is necessary to consider that herbivore densities may be affected both by wolf predation and by difficult to detect and measure costs of anti-predator behaviour. 

The Ecological Role of Wolves - photo 6

The Ecological Role of Wolves

The Ecological Role of Wolves. In turn, Hebblewhite and Smith investigate how herbivores may affect densities of plants and other animal species. In theory, these relationships could also work in a bottom-up pattern, from nutrients to plants to herbivores to predators. In practice, recent studies and reviews (Terborgh 2005, Schmitz 2006; reviewed by Borer et al. 2006), also including this book’s case studies on wolves, have found strong asymmetry and greater strength in top-down than in bottom-up forces. Thus, these findings support the notion that, by managing wolves, people manage or mismanage whole ecosystems.

The Ecological Role of Wolves - photo 7

The Ecological Role of Wolves

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