Thesis
Pronghorn: migration triggers and resource selection in southeastern Oregon
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/102506
Abstract
Pronghorn (Antilocapra americana) often migrate between distinct summer and winter ranges. Timing of transitions between seasonal ranges has been correlated with snow cover and some evidence suggests that changes in forage quality may also trigger migration in some areas. Seasonal home ranges and migratory routes are influenced by several landscape-level features including physiography, vegetation, and artificial barriers. In this study, I investigated the influence of snow and vegetation on the movements of 41 pronghorn fitted with very high frequency collars and 9 fitted with global positioning systems (GPS) collars. Snow cover and vegetation greenness, as evidenced by the Normalized Difference Vegetation Index (NDVI), were estimated using imagery generated by the moderate-resolution imaging spectroradiometer. I also investigated the influence of these 2 variables and 4 additional landscape features on habitat selection by the GPS-collared pronghorn. In both analyses I used a priori rules to evaluate seasonal groupings of pronghorn locations and the multiple response permutation procedure to test for differences between these groupings. Home ranges and migratory routes were delineated using the Brownian bridge movement model, and randomly placed home ranges and migratory routes quantified available resources for my investigation of resource selection. NDVI was higher and snow cover lower at observed radiolocations than at random locations throughout the study area. My Resource Selection Function also indicated pronghorn selected for areas with high NDVI. Pronghorn benefited by shifting from winter to summer home ranges and back again because NDVI was higher and snow cover lower on winter ranges during winter and higher on summer ranges during summer than conditions at the off-season home ranges. During these movements and when establishing seasonal home ranges, pronghorn avoided high elevations and land cover containing rocks and short sagebrush. Peak movements and spring and fall migration occurred when the best conditions shifted from winter to summer ranges and vice versa. Therefore, I suggest that both green-up of vegetation and snow conditions trigger spring migration of pronghorn in southeastern Oregon's Owyhee Region, and that snow conditions trigger fall migration back to these relatively flat ranges.
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Details
- Title
- Pronghorn
- Creators
- Kelsey Anne Dalton
- Contributors
- Lisa A. Shipley (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Agricultural, Human, and Natural Resource Sciences, College of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525146701842
- Language
- English
- Resource Type
- Thesis