Factors Influencing Seasonal Migrations of Pronghorn Across the Northern Sagebrush Steppe
Date
2015-10-07
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Abstract
Pronghorn (Antilocapra americana) undertake seasonal migrations and long-distance movements to satisfy annual life history requirements. To investigate these phenomena, 185 females were collared across the Northern Sagebrush Steppe (NSS) to classify migration and long-distance movement states and to analyze movement metrics. Based on 170 animal years, 55% of individuals undertook seasonal migrations. I also identified long-distance fawning-associated and driven movements during the study period. Thirty-six individuals used stopover sites during seasonal migration, principally during spring. During spring, migration was slow, sinuous and lengthy to exploit quality forage. During fall, fawning-associated and driven movements, movements were faster, more linear and shorter than spring. Both fall and spring stopover sites exhibited similar metrics, likely to profit from high quality forage areas. Next, I modelled multi-scalar migratory pathway selection in response to anthropogenic factors and environmental gradients. I found that pronghorn responded to road, well and hydrology variables at specific densities at finer scales. Generally, migratory pronghorn selected grasslands, intermediate slopes and south-facing aspects compared to other landcover types and topographic conditions. Pronghorn highly avoided increased well and road densities compared to lower densities of these features. Seasonal variation showed that during fall, pronghorn used large hydrologic systems while in spring pronghorn selected high quality forage areas. Pronghorn selected stopover sites with higher forage productivity values and lower densities of well attributes versus migratory pathways during both seasons. Relative to cultivated habitats, pronghorn avoided stopover sites in grassland or shrubland habitats versus migratory pathways. At finer scales, pronghorn slightly avoided anthropogenic features across the landscape, but at broader scales, pronghorn strongly selected against roads, natural resource wells and well drilling. I used a scale-integrated mapping approach to evaluate if such spatial predictions performed as well or better than single order scales to predict migration pathways. Finally, using scale-integrated spatial predictions, I assessed connectivity across the NSS to identify seasonal pronghorn connectivity networks. I concluded that multi-scale migration followed hierarchically nested theory where finer scale decisions are conditional on broader scales that can be assessed sequentially. I suggest that the pronghorn is a broad-scale focal species useful for designing conservation networks across the NSS.
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Ecology
Citation
Jakes, A. (2015). Factors Influencing Seasonal Migrations of Pronghorn Across the Northern Sagebrush Steppe (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26150