LAUSR

Pronghorn (Antilocapra americana) are an iconic wildlife species of sagebrush (Artemisia spp.) and grassland ecosystems in western North America. Over 50% of pronghorn have historically occurred in Wyoming; however, these populations have declined by nearly 30% in<2 decades, concurrent with expanding energy development and prolonged drought. Research suggests adult female pronghorn, unlike other temperate ungulates, are more likely to die in summer, when body condition is lower from extreme energetic demands of reproduction,which are higher for pronghorn thanother ungulates.To evaluate thepotential effects of intrinsic, environmental, and anthropogenic factors on summermortality risk, wemonitored 114 adult female pronghorn equippedwith global positioning system transmitters in theRedDesert regionof south-centralWyoming,USA between 2013 and 2015. We modeled mortality risk using Cox’s proportional hazards regression. Summer mortality risk was influenced by intrinsic and environmental factors; mortality risk increased when individuals were in poorer body condition entering the previous winter and when they experienced greater variation in average daily snowdepth during the previouswinter.Wedidnot detect an effect of the distance to anddensity of roads, oil andgaswells, or fences onpronghorn summermortality.During years of increasedwinter severitywith deep and fluctuating snow depths, managers may observe higher winter mortality and higher mortality the following summer, likely as a consequence of the energetic expense associated with winter survival and spring reproduction for female pronghorn. 2018 The Wildlife Society.