In the Rocky Mountains, bighorn sheep restoration has been only marginally effective; this iconic wilderness species currently exists at a fraction of their historic abundance and often in fragmented and small populations. To inform bighorn sheep conservation and restoration efforts, it is critical to understand sources of variation in key vital rates. Our objectives were to characterize the spatiotemporal variations and factors affecting survival and pregnancy rates of bighorn sheep (Ovis canadensis) using data from 19 bighorn sheep populations in Montana and Wyoming that occupied diverse landscapes ranging from the Northern Great Plains to the Rocky Mountains. We used a hierarchical modeling approach to estimate survival and pregnancy rates of adult females and identify the important intrinsic and environmental factors affecting these vital rates. Survival of prime‐aged animals was relatively high and stable, and pregnancy rates for prime‐aged animals showed more overall variation in response to intrinsic and extrinsic factors. Summer growing season, as indexed by integrated NDVI, positively influenced the probability of pregnancy and winter survival. This highlights the important relationship between summer growing season conditions and bighorn sheep physiological status. An index of mountain lion population abundance was related weakly to winter survival of bighorn sheep, with mountain lion abundance on winter ranges negatively affecting winter survival. Our results regarding the distribution of the estimated probabilities of pregnancy and survival, and the identification of factors associated with regional variability in these vital rates provide a foundation for understanding the dynamics of bighorn sheep populations in the Rocky Mountains. The importance of summer growing season conditions suggests management efforts should focus on maintaining and improving nutritional resources on bighorn sheep summer ranges, in efforts to enhance the condition of animals entering the breeding season and nutrient‐limited winter season. Although we document nontrivial changes in both pregnancy and winter survival rates associated with environmental variation, our results broadly support the dominant paradigm of ungulate demography insofar as survival rates of adult females were relatively higher and had less variation than pregnancy rates.

中文翻译：

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落基山大角羊妊娠和成活率的区域差异

在落基山脉，大角羊的修复仅起到了很小的作用。目前，这种标志性的荒野物种仅存于其历史丰富度的一小部分，并且通常处于零散的小种群中。为了告知大角羊保护和恢复工作，了解关键生命率变化的来源至关重要。我们的目标是表征大角羊（Ovis canadensis）的时空变异和影响生存率和妊娠率的因素）利用蒙大纳州和怀俄明州19个大角羊种群的数据，这些种群占据了从大平原北部到落基山脉的各种景观。我们使用分层建模方法来估计成年女性的存活率和妊娠率，并确定影响这些生命率的重要内在因素和环境因素。盛龄动物的存活率相对较高且稳定，盛龄动物的妊娠率在对内在和外在因素的反应中表现出更大的总体差异。根据综合NDVI指数，夏季生长季节对怀孕和冬季生存的可能性产生积极影响。这突出了夏季生长期条件与大角羊生理状态之间的重要关系。美洲狮的种群数量指数与大角羊的冬季生存能力之间存在弱关联，而冬季范围内的美洲狮种群数量对冬季生存能力产生负面影响。我们关于估计妊娠和生存概率分布的结果，以及与这些生命率中区域变异性相关的因素的识别，为了解落基山脉大角羊种群的动态提供了基础。夏季生长季节条件的重要性表明，管理工作应集中在维持和改善大角羊夏季范围的营养资源上，以努力改善进入繁殖季节和营养限制冬季的动物的状况。