Date of Award:

2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Advisor/Chair:

Eric M. Gese

Abstract

Cougars (Puma concolor) are elusive top-level predators and their predation patterns, particularly upon sensitive species, can be a source of concern to wildlife managers. Predation patterns, however, vary widely in accordance with differing landscape attributes, prey community composition, and preferences of individual cougars. The objective of this study was to better understand the impact of cougars upon their prey in the Pryor Mountains of Wyoming and Montana. Managers were concerned that cougar predation was having a negative impact upon a small, isolated Rocky Mountain bighorn sheep (Ovis canadensis canadensis) population and were hoping predation might be limiting a burgeoning feral horse population (Equus caballus).

With GPS collar data, we examined cougar kills (n = 200) to determine kill rates, prey composition, and selection for prey. Our findings indicated this population of cougars preyed primarily on mule deer (Odocoileus hemionus; 71.5%) but also included a substantial amount of bighorn sheep (8.0%) and other prey items (19.5%) in their diet. All bighorn kills were attributable to a specialist individual and we found no evidence of predation upon feral horses. 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.

To better understand the link between the risk of cougar predation and landscape attributes, we examined predation-specific resource selection by cougars. We first compared our set of confirmed kill sites to random sites at a fine scale (within 25 m of kill sites). We then built resource selection functions to conduct a coarse-scale analysis by using the 95% upper cut-off point of the known distances-dragged (94.9 m) to buffer caches sites, thereby creating zones of risk which had high probabilities of containing kill sites. We found that risk of cougar predation was associated with vegetation class and increased with decreasing horizontal visibility. For bighorn sheep, risk of predation was associated with juniper-mountain 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.

Included in

Biology Commons

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