Moose populations in the northeastern United States have declined over the past 15 years, primarily due to the impacts of winter ticks. Research efforts have focused on the effects of winter tick infestation on moose survival and reproduction, but stress and nutritional responses to ticks and other stressors remain understudied. We examined the influence of several environmental factors on moose calf stress hormone metabolite concentrations and nutritional restriction in Vermont, USA. We collected 407 fecal and 461 snow urine samples from 84 radio-collared moose calves in the winters of 2017–2019 (January–April) to measure fecal glucocorticoid metabolites (fGCM) concentrations and urea nitrogen:creatinine (UN:C) ratios. We used generalized mixed-effects models to evaluate the influence of individual condition, winter ticks, habitat, climate and human development on stress and nutrition in calf moose. We then used these physiological data to build generalized linear models to predict calf winter survival. Calf fGCM concentrations increased with nutritional restriction and snow depth during adult winter tick engorgement. Calf UN:C ratios increased in calves with lighter weights and higher tick loads in early winter. Calf UN:C ratios also increased in individuals with home ranges composed of little deciduous forests during adult winter tick engorgement. Our predictive models estimated that winter survival was negatively related to UN:C ratios and positively related to fGCM concentrations, particularly in early winter. By late March, as winter ticks are having their greatest toll and endogenous resources become depleted, we estimated a curvilinear relationship between fGCM concentrations and survival. Our results provide novel evidence linking moose calf stress and nutrition, a problematic parasite and challenging environment and winter survival. Our findings provide a baseline to support the development of non-invasive physiological monitoring for assessing environmental impacts on moose populations.

中文翻译：

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与冬季蜱、景观特征、气候介导因素和生存相关的幼年驼鹿压力和营养动态

在过去的 15 年中，美国东北部的驼鹿种群数量有所下降，这主要是由于冬季蜱虫的影响。研究工作集中在冬季蜱虫侵扰对驼鹿生存和繁殖的影响，但对蜱虫和其他压力源的压力和营养反应仍未得到充分研究。我们研究了美国佛蒙特州几种环境因素对驼鹿应激激素代谢物浓度和营养限制的影响。我们在 2017 年至 2019 年冬季（1 月至 4 月）从 84 头无线电项圈的驼鹿犊中收集了 407 份粪便和 461 份雪尿样本，以测量粪便糖皮质激素代谢物 (fGCM) 浓度和尿素氮：肌酐 (UN:C) 比率。我们使用广义混合效应模型来评估个体条件、冬季蜱、栖息地、气候和人类发展对小驼鹿压力和营养的影响。然后，我们使用这些生理数据建立广义线性模型来预测小牛的冬季存活率。在成年冬季蜱充血期间，犊牛 fGCM 浓度随着营养限制和雪深而增加。初冬体重较轻和蜱负荷较高的小牛 UN:C 比率增加。在成年冬季蜱虫充血期间，家庭范围由小落叶林组成的个体中，犊牛 UN:C 比率也有所增加。我们的预测模型估计，冬季存活率与 UN:C 比率呈负相关，与 fGCM 浓度呈正相关，尤其是在初冬。到 3 月下旬，随着冬季蜱虫的死亡人数最多，内源性资源枯竭，我们估计了 fGCM 浓度和存活率之间的曲线关系。我们的研究结果提供了新的证据，将驼鹿小牛的压力和营养、有问题的寄生虫和具有挑战性的环境以及冬季生存联系起来。我们的研究结果为支持开发非侵入性生理监测以评估环境对驼鹿种群的影响提供了基线。