Large herbivores exhibit relatively slow-paced life histories, and allocate resources toward maintaining high rates of adult survival, while juvenile survival has greater variability. Maternal females make decisions throughout life stages of reproduction to meet their nutritional demands while simultaneously ensuring survival and recruitment of young to maximize fitness. We investigated tradeoffs associated with resource selection by mule deer (Odocoileus hemionus) surrounding stages of reproduction in Mojave National Preserve, CA, United States. To understand potential tradeoffs associated with offspring survival and maternal nutritional condition, we measured differences in patterns of resource selection among pre-parturient females, females provisioning young, and females following the loss of young. The third trimester of gestation and lactation are considered the most nutritionally demanding stages of reproduction. We hypothesized that energetic costs would change rapidly throughout those stages of reproduction, especially after the loss of an offspring. Further, we hypothesized that lactating females would balance the acquisition of nutritional sources with safety of young. We used radio-collar and randomly generated locations to model resource selection in a hierarchical approach utilizing machine learning algorithms and traditional resource selection functions (RSFs). We also monitored recruitment of young born to GPS-collared females using VHF radio-collars equipped with mortality indicators. During all three stages of reproduction, adult females selected greater NDVI, less rugged terrain, areas close to water (especially while provisioning offspring), and higher elevations. Selection for greater levels of NDVI was stronger pre-parturition and following the loss of offspring compared to when females were provisioning offspring. We also observed high variation toward the selection of NDVI among individual females while provisioning young, which was less pronounced during the other reproductive stages. Offspring survival during our study was positively associated with females that selected greater levels of NDVI. Further, we were not able to detect a tradeoff between safety of young (ruggedness) and nutrient acquisition (NDVI). Perhaps predation risk and nutritional resources are not mutually exclusive in this ecosystem; and, females may be able to balance reproductive investment with the ability to select for water and nutrition while simultaneously ensuring lower risk of predation for themselves and their offspring.

中文翻译：

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平衡当前和未来的生殖投资：长寿草食动物生殖阶段资源选择的变化

大型食草动物表现出相对慢节奏的生活史，并将资源分配给维持高成鱼存活率，而幼鱼的存活率具有更大的可变性。母性女性在生殖的整个生命阶段做出决定以满足其营养需求，同时确保幼崽的生存和招募以最大限度地提高健康。我们调查了与美国加利福尼亚州莫哈韦国家保护区的骡鹿 (Odocoileus hemionus) 周围繁殖阶段的资源选择相关的权衡。为了了解与后代存活和母体营养状况相关的潜在权衡，我们测量了产前雌性、提供幼仔的雌性和失去幼仔后的雌性之间资源选择模式的差异。妊娠晚期和哺乳期被认为是营养需求最高的繁殖阶段。我们假设能量消耗会在繁殖的这些阶段迅速变化，尤其是在失去后代之后。此外，我们假设哺乳期女性会在营养来源的获取与年轻人的安全之间取得平衡。我们使用无线电项圈和随机生成的位置，利用机器学习算法和传统资源选择功能 (RSF) 以分层方法对资源选择进行建模。我们还使用配备死亡率指标的 VHF 无线电项圈监测了佩戴 GPS 项圈的女性出生的年轻人的招募情况。在繁殖的所有三个阶段，成年雌性选择较大的 NDVI、较不崎岖的地形、靠近水的地区（特别是在提供后代时）和更高的海拔。与雌性提供后代时相比，在分娩前和后代丧失后对更高水平 NDVI 的选择更强。我们还观察到个体雌性个体在提供幼体时选择 NDVI 的高度变化，这在其他生殖阶段不太明显。我们研究期间的后代存活率与选择更高水平 NDVI 的雌性呈正相关。此外，我们无法检测到年轻人的安全性（坚固性）和营养获取（NDVI）之间的权衡。也许在这个生态系统中，捕食风险和营养资源并不相互排斥；和，