Chapter 21 Changes in Elk Resource Selection and Distribution with the Reestablishment of Wolf Predation Risk

Abstract

Theme How animals use resources at local and landscape scales can differ depending on whether starvation is the primary limiting factor or significant predation risk also exists. With predation, individuals face the added and often conflicting demands of obtaining adequate nutrition while reducing predation risk. However, disentangling differences between the respective resource selection strategies in a given system is rarely possible. We evaluated changes in resource selection and prey distribution for a non-migratory elk population formerly limited by winter starvation and now subjected to wolf predation in the Madison headwaters area of Yellowstone National Park. Analyses of elk resource selection prior to wolf establishment (1991–1992 through 1997–1998) demonstrated a dynamic spatial and temporal response to changes in snow pack at the local and landscape level, with elk selecting areas with low snow mass, but forced to occupy areas with higher local snow mass as conditions on the winter range became more severe ( Chapter 8 by Messer et al. , this volume). We hypothesized that variables affecting elk resource selection prior to wolves would retain their primacy in post-wolf models (1998–1999 through 2005–2006), but that the magnitude of each would change depending on its contribution to predation risk. Broad-scale changes in prey distribution could also occur if the collective attributes of a landscape serve to alternately provide areas with decreased or increased predation risk. Thus, we also evaluated the potential for landscape-scale shifts in the distribution of the elk population among the three drainages of the Madison headwaters area if elk selected distinct prey refuges and avoided areas where they were particularly vulnerable to wolf predation. Alternatively, elk distribution shifts among the three drainages could also result from differential predation risk with lower densities of animals in high risk areas due to the removal by wolves of substantial numbers of prey.