Scholarship & Research
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Item Is habitat constraining bighorn sheep distribution and restoration: a case study in the Greater Yellowstone Ecosystem(Montana State University - Bozeman, College of Letters & Science, 2019) Lula, Ethan Shawn; Chairperson, Graduate Committee: Robert A. GarrottRocky Mountain Bighorn Sheep (Ovis canadensis) restoration continues to be a challenge throughout western North America despite nearly a century of efforts dedicated to the species' recovery. A persistent problem for restoration is populations failing to expand into surrounding areas of habitat even during years of population growth. While populations can be constrained by several environmental factors and behavioral tendencies, we contend habitat availability is not the primary limiting factor. This study incorporated GPS data from bighorn sheep within the Taylor-Hilgard population in the Madison Mountain Range, located in the northwestern extent of the Greater Yellowstone Ecosystem (GYE), to develop summer and winter resource selection function (RSF) habitat models. The objective of this study was to evaluate a hypothesis that habitat was not the primary factor limiting distributions of bighorn sheep within the Madison Range by developing biologically-plausible RSF models and using covariates expected to influence selection. Multiple functional forms and spatial grains for covariates were considered and sets of summer and winter resource selection models compared using AIC subscript c. Results indicated that bighorn sheep resource selection was grain dependent, with bighorn sheep generally selecting covariates at the larger 500 m and 1,000 m spatial grains. Summer selection was characterized by rugged terrain, steep slopes, reduced canopy cover, southwestern aspects and ridgelines. Winter selection was characterized by low elevations, southwestern aspects, steep slopes, reduced canopy cover, ridgelines, high summer NDVI amplitude, and areas close to steep terrain (slopes > or = 45°). Predicted winter habitat occurred in a non-contiguous distribution primarily along low-elevation, southwest-facing aspects within the Madison Valley, and predicted summer habitat was concentrated along high elevation ridgelines. Model results were successfully validated using independent GPS data. Potential abundance for the Madison Range was estimated by linking the winter RSF to population estimates for the Taylor Hilgard and results suggested that the Range may be capable of supporting 2 to 4 times the number of bighorn sheep currently estimated. Study results supported the hypothesis that habitat was not the primary factor limiting extant bighorn sheep populations, suggesting that broader distributions within the Range are possible if novel restoration strategies are considered.Item Spatiotemporal patterns of resource use and density of American black bears on Yellowstone's northern range(Montana State University - Bozeman, College of Letters & Science, 2020) Bowersock, Nathaniel Roth; Chairperson, Graduate Committee: Andrea Litt; Andrea R. Litt, Kerry A. Gunther, Jay J. Rotella, Jerod A. Merkle and Frank T. van Manen were co-authors of the article, 'Influence of resource waves on American black bears during Spring in the northern range of Yellowstone National Park' which is contained within this thesis.; Andrea R. Litt, Kerry A. Gunther, Michael A. Sawaya, Jay J. Rotella and Frank T. van Manen were co-authors of the article, 'Factors associated with varying density of black bears on Yellowstone National Park's northern range' which is contained within this thesis.The availability of resources, such as food and cover, can directly influence the movement and distribution of wildlife populations. The abundance and seasonal timing of many resources have changed in Yellowstone National Park (YNP), which has influenced populations of American black bears (Ursus americanus), an opportunistic omnivore. Previous studies have focused on how changes in resources have influenced black bears in the central and southern regions of YNP, however little work has focused on black bears in the northern part of the park. In 2017-2018, we used GPS collars and non-invasive genetic sampling to understand resource selection and variation in densities of black bears on the Northern Range. We sought to 1) assess whether black bears were following seasonal pulses of resources (resource waves) in the spring, such as the green wave and elk (Cervus canadensis) calving wave and 2) evaluate how densities of black bears varied based on landscape features, generating a baseline abundance estimate to help track changes in the population over time. We found evidence that black bears followed the green wave, prioritizing forage quality over quantity when selecting patches of green vegetation in early spring. However, black bears were less likely to select areas near historical elk calving grounds, suggesting that consumption of neonates is more opportunistic. Densities of black bears varied among vegetation communities, with the highest densities in forested communities dominated by Douglas fir. Our study provides the first baseline density estimates for black bears on the Northern Range, with an average density of 12.8 bears/100km 2 (95% CI = 9.4 - 17.5), which is higher than other regions in YNP. Availability of high-quality resources may allow for higher densities of black bears, with potential ramifications for other wildlife populations on the Northern Range. Information about resource selection and variation in estimated densities could be used to guide management decisions to continue to reduce human-bear conflicts and provide safe wildlife viewing experiences for the growing number of visitors to YNP.Item Behavior and environmental selection by elk (Cervus canadensis nelsoni) during summer and fall in the first and second Yellow Mule drainages, Madison County, Montana(Montana State University - Bozeman, College of Agriculture, 1975) Joslin, Gayle LynneItem Accumulation of dietary methylmercury by walleye and white crappie in the Tongue River Reservoir, Montana(Montana State University - Bozeman, College of Agriculture, 1982) Knight, Denise ElaineItem Elk (Cervus elaphus) vigilance levels in response to predation risk from wolves (Canis lupus)(Montana State University - Bozeman, College of Letters & Science, 2007) Liley, Stewart Grayson; Chairperson, Graduate Committee: Scott CreelMany studies have shown that levels of antipredator vigilance are sensitive to variation in prey attributes, such as age, sex and group size. It is also well established that vigilance is sensitive to environmental effects, such as the presence of cover. In contrast, little is known about the sensitivity of vigilance to variation in factors associated with the predator itself, such as proximity, the size of the threatening group, and cues about motivation to hunt. Finally, little is known about the relative importance of these three classes of variables (predator, prey, and environment), or about the information content of simple versus complex models of vigilance. We quantified the vigilance levels of elk (Cervus elaphus) preyed upon by wolves (Canis lupus) in Yellowstone National Park, between January and May in 2005 and 2006, and compared a set of 38 regression models for vigilance levels, using Akaike's Information Criterion.