It is important to understand the physiological stressors in animals especially for threatened species or intensively managed to improve their conservation and optimise their reproduction. We sought to understand changes in stress hormones (faecal glucocorticoid metabolites) in black rhinoceros (Diceros bicornis michaeli) in relation to population density and sex (intrinsic factors) and plant minerals, rainfall and land surface temperature (extrinsic factors). We used non-invasive faecal sampling techniques on animals of known sex, age and dominance in seven populations of contrasting population densities over 1 year. We measured variability in faecal corticosterone metabolites through radioimmunoassay and related them to population density, sex and faecal calcium, phosphorus, copper, zinc and potassium as characteristic of plant minerals, rainfall and temperature. We used linear mixed models (LMM) to analyse the data. We did not detect a significant relationship between physiological stress parameters and population density. However, we have indications that stress levels increased as rainfall and temperature increased and were correlated negatively and positively with concentration of faecal phosphorus and copper respectively; we found higher stress levels in females than in males. These results suggest that both intrinsic and extrinsic factors explain the variation in physiological stress observed in black rhinoceros.

中文翻译：

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东部黑犀牛 (Diceros bicornis michaeli) 的生理应激受其密度、气候变量和性别的影响

了解动物的生理应激源非常重要，特别是对于受威胁物种或集中管理的物种，以改善其保护并优化其繁殖。我们试图了解黑犀牛（Diceros bicornis michaeli）应激激素（粪便糖皮质激素代谢物）的变化与种群密度和性别（内在因素）以及植物矿物质、降雨量和地表温度（外在因素）的关系。我们在一年多的时间里对七个具有对比种群密度的种群中已知性别、年龄和优势的动物使用了非侵入性粪便采样技术。我们通过放射免疫测定法测量了粪便皮质酮代谢物的变异性，并将其与人口密度、性别以及作为植物矿物质特征的粪便钙、磷、铜、锌和钾、降雨量和温度相关联。我们使用线性混合模型（LMM）来分析数据。我们没有发现生理应激参数与人口密度之间存在显着关系。然而，我们有迹象表明，压力水平随着降雨量和温度的增加而增加，并分别与粪便中磷和铜的浓度呈负相关和正相关；我们发现女性的压力水平高于男性。这些结果表明内在和外在因素都可以解释黑犀牛中观察到的生理应激的变化。