DISSERTATION RESEARCH: The influence of parasite load on glucocorticoid hormone levels: An experimental assessment in a natural setting

应激激素（糖皮质激素）是生态学家非常感兴趣的，因为它们影响动物的健康和生存，并提供了一个直接的，可量化的亚致死压力指数。已知基线糖皮质激素水平与脊椎动物的年龄、性别和社会等级相关。然而，糖皮质激素水平和自由放养动物及其环境的内在因素之间几乎没有因果关系。由于糖皮质激素可以增强或抑制免疫系统，因此预计压力激素和寄生虫之间存在相互作用。这项研究将确定大型寄生虫和压力之间的关系的性质，使用糖皮质激素水平作为压力的指标，在一个共同的，自由放养的哺乳动物。本研究的目的是量化基线粪便糖皮质激素水平，并将其与动物特征（例如，年龄、性别）和寄生虫负荷，实验性地减少体外寄生虫和蠕虫，以测试糖皮质激素水平和寄生虫负荷之间的因果关系，并确定寄生虫减少个体的糖皮质激素水平是否影响随后的寄生虫获得。动物体内的糖皮质激素浓度越来越多地被用于评估野生动物的健康状况，对环境的反应，并影响管理决策。为了使这些决定最有效，我们必须确定对基线压力值重要的因素。这项研究将确定常见寄生虫对内分泌系统的影响，以及基线糖皮质激素水平是否使个体易于感染。在实验环境中评估这种相互作用将提高我们理解动物压力的能力，并在疾病和压力成为关注问题时做出明智的管理决策。更广泛的影响包括对学生的培训和教育。这个项目的所有要素将被纳入本科生的野生动物疾病生态学课程。学生将参加体验式学习练习，让他们在实验室和现场会议期间参与项目的各个方面。

Stress hormones (glucocorticoids) are of great interest to ecologists because they impact animal fitness and survival and provide a direct, quantifiable index of sublethal stress. Baseline glucocorticoid levels are known to be correlated with age, sex, and social rank of vertebrates. However, few causal relationships have been established between glucocorticoid levels and factors intrinsic to free-ranging animals and their environment. Interactions between stress hormones and parasites are predicted to exist because glucocorticoids can enhance or depress the immune system. This study will determine the nature of the relationship between macroparasites and stress, using glucocorticoid levels as an indicator of stress, in a common, free-ranging mammal. Objectives of this research are to quantify baseline fecal glucocorticoid levels and correlate those with animal characteristics (e.g., age, sex) and parasite burden, experimentally reduce ectoparasites and helminths to test causal relationships between glucocorticoid levels and parasite burden, and determine if glucocorticoid levels of parasite-reduced individuals influence subsequent parasite acquisition. Glucocorticoid concentrations in animals are increasingly being used to evaluate wildlife health, responses to their environment, and influence management decisions. For such decisions to be most effective it is imperative that we identify factors important to baseline stress values. This study will determine the influence of common parasites on the endocrine system and if baseline glucocorticoid levels predispose individuals to infection. Evaluating such interactions in an experimental context will enhance our ability to understand animal stress and make informed management decisions when disease and stress are issues of concern. Broader impacts include the training and education of students. All elements of this project will be incorporated into a wildlife disease ecology course for undergraduates. Students will participate in experiential learning exercises that involve them in all aspects of the project during lab and field sessions.