Data from: Noninvasive physiological markers demonstrate link between habitat quality, adult sex ratio and poor population growth rate in a vulnerable species, the Cape mountain zebra

Effective conservation and species management requires an understanding of the causes of poor population growth. Conservation physiology uses biomarkers to identify factors that contribute to low individual fitness and population declines. Building on this, macrophysiology can use the same markers to assess how individual physiology varies with different ecological or demographic factors over large temporal and spatial scales. Here, we use a macrophysiological approach to identify the ecological and demographic correlates of poor population growth rates in the Cape mountain zebra metapopulation. We use two non-invasive biomarkers: faecal glucocorticoids as a measure of chronic stress, and faecal androgens as an indicator of male physiological status. We found that faecal glucocorticoid concentrations were highest in the spring prior to summer rainfall, and were elevated in individuals from populations associated with low quality habitat (lower grass abundance). In addition, faecal androgen concentrations were higher in populations with a high proportion of non-breeding stallions (where male:female adult sex ratios exceed 2:1) suggesting sex ratio imbalances may intensify male competition. Finally, population growth rate was negatively associated with faecal glucocorticoid concentrations and female fecundity was negatively associated with faecal androgens, indicating a relationship between hormone profiles and fitness. Together, our results provide cross population evidence for how poor population growth rates in Cape mountain zebra can be linked to individual physiological biomarkers. More broadly, we advocate physiological biomarkers as indicators of population viability, and as a way to evaluate the impact of variable ecological and demographic factors. In addition, conservation physiology can be used to assess the efficacy of management interventions for this subspecies, and this approach could inform models of species’ responses to future environmental change.有效的物种保护与管理工作，需要明晰种群增长乏力的根源。保护生理学（conservation physiology）借助生物标志物（biomarkers），可识别导致个体适合度下降与种群衰退的各类因素。在此基础上，宏生理学（macrophysiology）可依托同一类标志物，在较大的时空尺度上，评估个体生理状态如何随不同生态或人口统计因素发生变化。 本研究采用宏生理学方法，旨在明确开普山斑马（Cape mountain zebra）集合种群（metapopulation）中，种群增长速率低下所关联的生态与人口统计因素。本研究选用两种非侵入式生物标志物：以粪便糖皮质激素（faecal glucocorticoids）作为慢性应激（chronic stress）水平的检测指标，以粪便雄激素（faecal androgens）反映雄性个体的生理状态。 研究结果显示，粪便糖皮质激素浓度在夏季降雨前的春季达到峰值，且来自低质量栖息地（草本丰度较低）种群的个体，其粪便糖皮质激素浓度显著升高。此外，当种群中非繁殖种马的占比较高（成年雌雄比超过2:1）时，粪便雄激素浓度更高，这表明性比失衡可能加剧雄性间的竞争。最后，种群增长速率与粪便糖皮质激素浓度呈负相关，而雌性繁殖力（female fecundity）与粪便雄激素浓度同样呈负相关，这提示激素谱与个体适合度之间存在关联。 综上，本研究结果为开普山斑马种群增长乏力与个体生理生物标志物之间的关联提供了跨种群证据。从更广泛的意义上来说，本研究支持将生理生物标志物作为种群生存力（population viability）的评估指标，以及用于量化可变生态与人口统计因素影响的工具。此外，保护生理学可用于评估该亚种各类管理干预措施的有效性，该研究方法也可为预测物种对未来环境变化的响应模型提供参考依据。