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Nebraska’s pronghorn population has been stable over the last decade, yet their presence on the landscape remains a contentious subject amongst private landowners. Conversion of grassland for crop production and increased anthropogenic activity has drastically altered pronghorn behavior throughout their current range, however basic ecology and resource use by pronghorn in Nebraska remains poorly understood. Establishing baseline population metrics and seasonal patterns of resource use for this population at the eastern periphery of the species range is critical to guide management actions. We deployed GPS collars on 110 adult pronghorn to quantify survival, mortality risk, and seasonal resource selection in western Nebraska. We used Kaplan-Meier and Cox Proportional Hazards modeling approaches to calculate adult survival and mortality risk. We found that annual survival was 0.65 (95% CI: 0.58-0.73), survival significantly decreased in autumn, and mortality risk was 2.36 (95% CI: 1.32-4.23; P = 0.004) times higher for males than females. To investigate seasonal resource selection, we used a Step Selection Function approach, which uses conditional logistic regression to compare predictor variables at used and available GPS locations. Seasons were delineated as winter (1 Dec-28 Feb), spring (1 Mar-31 May), summer (1 Jun-31 Aug), and autumn (1 Sept-30 Nov). Used locations showed no movement across Interstate 80 and habitat composition differed on either side so we evaluated resource selection separately between the herds north and south of the interstate. Our models included 2-way interactions with sex to determine if sexual segregation played a role in selection. We evaluated selection of grassland/herbaceous land cover, agricultural land, human development, distance to water, and distance to roads. Pronghorn selected cropland and avoided human development regardless of herd, sex, or season. Use of cropland was disproportionate to its availability on the landscape. Selection or avoidance of roads and water varied across herd, sex, and season. This work begins the complex task of understanding pronghorn ecology in an agricultural system. Our research provides valuable insight into the factors influencing population dynamics so that biologists can implement effective strategies to manage pronghorn populations in western Nebraska.
Advisor: Andrew R. Little
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