Date of Award:

5-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Eric M. Gese

Committee

Eric M. Gese

Committee

Michael L. Wolfe

Committee

Toni K. Ruth

Abstract

We conducted this study to better understand the impact of cougar (Puma concolor) predation in the Pryor Mountains of Wyoming and Montana. Managers of the Bighorn Canyon National Recreation Area and the Pryor Mountain Wild Horse Range were concerned that cougars were having a negative impact upon a small, isolated Rocky Mountain bighorn sheep (Ovis canadensis canadensis) population and were hoping predation might be limiting a feral horse population (Equus caballus) that was in excess of the Appropriate Management Level set by the Bureau of Land Management. Wildlife tourism brings revenue to the park and the surrounding communities making the status of these herds an economic, as well as an ecological and social, concern.

We captured and GPS-collared cougars and examined their kills to determine kill rates, prey composition, and selection for prey. Our findings indicated this population of cougars preyed primarily on mule deer (Odocoileus hemionus) but also included a substantial amount of bighorn sheep and other prey items in their diet. All bighorn kills were attributable to a specialist individual and we found no evidence of predation upon feral horses. These results showed that, while cougar predation was not limiting the feral horse population, at times, predation could be one of a host of factors limiting the bighorn sheep population.

Cougars are an ambush predator and must approach to within a close distance of prey items undetected to achieve a successful kill. Consequently, there is a relationship between cougar predation and landscape attributes such as horizontal visibility, slope, vegetation class, and ruggedness. To better understand the link between the risk of cougar predation and landscape attributes we examined predation-specific habitat selection by cougars at fine and coarse scales. After making a kill, cougars typically drag their prey items to a cache site where they consume their kill and, therefore, it is often impossible to identify specific kill sites. When possible we backtracked from cache sites to kill sites and used a fine-scale analysis to compare landscape characteristics within the immediate vicinity of these confirmed kill sites to those of random sites. For our coarsescale analysis of predation risk we utilized our entire dataset of kills by using the typical distances-dragged to buffer caches sites, thereby creating zones of risk which had high probabilities of containing kill sites. We modeled risk of cougar predation by constructing resource selection functions for these zones of risk. We found that risk of predation was associated with vegetation class and increased with decreasing horizontal visibility. For bighorn sheep, risk of cougar predation was associated with junipermountain mahogany (Juniperus spp., Cercocarpus ledifolius) woodlands. We recommend managers thin junipers to increase horizontal visibility in areas where the juniper-mountain mahogany vegetation class intersects bighorn sheep habitat.

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