Pronghorn (Antilocapra americana) occur throughout western North America. In Idaho, USA, following intensive hunting to reduce crop depredations in the late 1980s, pronghorn populations have not rebounded to desired levels. Because neonatal survival in ungulates is one factor limiting population growth, we evaluated cause‐specific mortality and the influence of intrinsic and extrinsic factors on survival rates of 217 radio‐collared pronghorn fawns across 3 study areas in Idaho during 2015–2016. For intrinsic variables, we determined the sex and body mass index (BMI) for each fawn. For extrinsic variables, we determined the abundance of predators and alternate prey, estimated the normalized difference vegetation index (NDVI) for 1 month pre‐ and post‐parturition, and measured fecal nitrogen and diaminopimelic acid (DAPA). We considered NDVI as a measure of plant productivity, and fecal nitrogen and DAPA as possible proxies of diet quality. We predicted NDVI, fecal nitrogen, and DAPA would be positively related to the nutritional status of females and positively related to fawn survival. We used Program MARK with known fate models to estimate semi‐monthly survival rates of pronghorn fawns for the first 4 months post‐parturition. During both years, the leading cause of fawn mortality was coyote (Canis latrans) predation (58%), followed by unknown causes of mortality (18%), unknown predation (12%), predation by bobcats (Lynx rufus; 6%), predation by golden eagles (Aquila chrysaetos; 3%), and other (3%). Mean fawn survival for the 4 months post‐parturition across years and study sites was 0.42 ± 0.04 (SE; range = 28–62%). The top survival model included BMI, lagomorph abundance, and DAPA and had a model weight of 83.3%. All 3 variables were positively related to pronghorn fawn survival. Because females with increased nutrition generally have heavier fawns, BMI was likely correlated to diet quality, which was supported by the positive relationship between DAPA and fawn survival. We hypothesize that high lagomorph abundance created an alternate prey base to buffer coyotes from preying on pronghorn neonates. We found no influence of measures of NDVI (pre‐ and post‐parturition), fecal nitrogen, or predator abundance on fawn survival. Management actions providing high‐quality forage for pronghorn are likely to contribute to production of heavier fawns having the highest chance of survival. © 2020 The Wildlife Society.

中文翻译：

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影响爱达荷州叉角羚小鹿成活率的因素

叉角羚（Antilocapra americana）发生在整个北美西部。在美国爱达荷州，为了减少农作物的砍伐，在1980年代后期进行了广泛的狩猎之后，叉角羚的种群数量尚未反弹至理想水平。由于有蹄类动物的新生儿存活是限制种群增长的一个因素，因此我们评估了爱因荷州3个研究区域在2015–2016年间特定原因的死亡率以及内在和外在因素对217只放射性领叉角羚小鹿存活率的影响。对于内在变量，我们确定了每只小鹿的性别和体重指数（BMI）。对于外部变量，我们确定了捕食者和替代猎物的数量，估计了分娩前后1个月的标准化差异植被指数（NDVI），并测量了粪便氮和二氨基庚二酸（DAPA）。我们将NDVI视为衡量工厂生产力的指标，粪便氮和DAPA可能是饮食质量的代表。我们预测NDVI，粪便氮和DAPA与女性的营养状况呈正相关，与小鹿的存活呈正相关。我们使用带有已知命运模型的Program MARK估计了分娩后前4个月叉角小鹿的半月生存率。在这两年中，小鹿死亡率的主要原因是土狼（犬天牛（58％），其次是死因未知（18％），天敌（12％），山猫（天猫座rufus； 6％），金鹰（Aquila chrysaetos; 3％），其他（3％）。多年和研究地点在分娩后4个月的平均小鹿存活率为0.42±0.04（SE；范围= 28-62％）。生存率最高的模型包括BMI，lagomorph丰度和DAPA，模型权重为83.3％。所有3个变量均与叉角羚的存活率正相关。由于营养增加的雌性通常有较重的小鹿，因此BMI可能与饮食质量相关，这是DAPA与小鹿存活之间呈正相关的结果。我们假设高的鼠尾草丰度创造了一个替代的猎物基础，以缓冲土狼对叉角羚新生儿的捕食。我们没有发现分娩前和产后NDVI，粪便氮或捕食者的丰度对小鹿存活率的影响。为叉角羚提供优质饲料的管理措施可能有助于生产具有最高生存机会的较重小鹿。©2020野生动物协会。