DISSERTATION RESEARCH: Indirect Effects of Predators on Prey: Consequences of Wolf Predation for Elk behavio, Nutrition, and Reproduction

Montana State University, Bozeman MT

Investigators

Abstract

The total impact of predators on prey populations includes the killing of prey and the less conspicuous costs associated with antipredator behavior. These costs often affect prey survival or reproduction and can be an important part of population dynamics in experiments. However, uncovering the costs of these behaviors in the wild is difficult because predation risk tends to vary unpredictably over time and space. Federal wolf reintroduction and conservation programs have resulted in rapidly growing and widely expanding populations in several areas of North America. These new wolf populations have generated several highly publicized controversies, especially in landscapes where animals preyed upon by wolves provide an important source of recreation and revenue for local communities. In the Gallatin Canyon of Montana, elk population size and recruitment showed significantly depressed levels immediately following recolonization by wolves, and direct predation appears only partly responsible. Although winter survival may be involved, pregnancy rates and calf survival suggest elk reproduction might also be influenced by the recent arrival of wolves. This study has shown that elk will break into smaller groups, spend more time in conifer forest, move to higher elevations, increase their level of vigilance, and decrease grazing in open areas when wolves are nearby. Thus, costs associated with avoiding wolves likely exist and are probably an important factor for elk populations. This study will record foraging behavior, diet composition, and dietary nutrition in three separate herds of elk as wolves move across the Gallatin Canyon throughout the winter. Daily wolf locations and frequency of kills will be monitored so that behavioral and nutritional data for each elk herd can be linked to differing levels of predation risk. Finally, differences in condition, survival, and reproductive success between elk herds will be associated with behavioral responses to wolves. In addition to providing financial support for a graduate student to complete the work and an educational experience for undergraduates, these data will contribute substantially to our understanding of the role of antipredator behavior in population dynamics under natural variation in risk.