Invasive species can exert rapid depletion of resources after introduction and, in turn, affect their own population density. Additionally, management actions can have direct and indirect effects on demography. Physiological variables can predict demographic change but are often restricted to snapshots-in-time and delayed confirmation of changes in population density reduces their utility. To evaluate the relationships between physiology and demography, we assessed metrics of individual and demographic stress (baseline and 1-h corticosterone (CORT), body condition and bacterial killing ability) in the invasive snake Boiga irregularis on Guam collected in intervals of 10–15 years. We also assessed potential discrepancies between different methods of measuring hormones [radioimmunoassay (RIA) versus enzyme immunoassay (EIA)]. The magnitude of difference between RIA and EIA was negligible and did not change gross interpretation of our results. We found that body condition was higher in recent samples (2003 and 2018) versus older (1992–93) samples. We found corresponding differences in baseline CORT, with higher baseline CORT in older, poorer body condition samples. Hormonal response to acute stress was higher in 2018 relative to 2003. We also found a weak relationship between circulating CORT and bacterial killing ability among 2018 samples, but the biological significance of the relationship is not clear. In an effort to develop hypotheses for future investigation of the links between physiology and demography in this and other systems, we discuss how the changes in CORT and body condition may reflect changes in population dynamics, resource availability or management pressure. Ultimately, we advocate for the synchronization of physiology and management studies to advance the field of applied conservation physiology.

中文翻译：

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了解入侵历史背景下的压力指标：以棕色树蛇 (Boigaregularis) 为例

入侵物种在引入后会迅速消耗资源，进而影响其自身的种群密度。此外，管理行动可能对人口结构产生直接和间接的影响。生理变量可以预测人口变化，但通常仅限于即时快照，并且延迟确认人口密度变化会降低其效用。为了评估生理学和人口统计学之间的关系，我们评估了关岛侵入性蛇 Boigaregularis 的个体和人口压力指标（基线和 1 小时皮质酮 (CORT)、身体状况和细菌杀灭能力），以 10-15 的间隔收集年。我们还评估了测量激素的不同方法[放射免疫测定 (RIA) 与酶免疫测定 (EIA)] 之间的潜在差异。RIA 和 EIA 之间的差异幅度可以忽略不计，并没有改变我们对结果的总体解释。我们发现，最近的样本（2003 年和 2018 年）与较旧的样本（1992-93 年）相比，身体状况更高。我们发现基线 CORT 存在相应差异，在年龄较大、身体状况较差的样本中基线 CORT 较高。相对于 2003 年，2018 年对急性压力的荷尔蒙反应更高。我们还在 2018 年样本中发现循环 CORT 与细菌杀灭能力之间的关系较弱，但该关系的生物学意义尚不清楚。为了为未来研究该系统和其他系统中生理学和人口统计学之间的联系建立假设，我们讨论了 CORT 和身体状况的变化如何反映人口动态的变化，资源可用性或管理压力。最终，我们提倡生理学和管理学研究同步推进应用保护生理学领域。