Climate induced stress and mortality in vervet monkeys

As the effects of global climate change become more apparent, animal species will become increasingly affected by extreme climate and its effect on the environment. There is a pressing need to understand animal physiological and behavioural responses to climatic stressors. We used the reactive scope model as a framework to investigate the influence of drought conditions on vervet monkey (Chlorocebus pygerythrus) behaviour, physiological stress and survival across 2.5-years in South Africa. Data were collected on climatic, environmental and behavioural variables and physiological stress via faecal glucocorticoid metabolites (fGCMs). There was a meaningful interaction between water availability and resource abundance: when food availability was high but standing water was unavailable, fGCMs were higher compared to when food was abundant and water was available. Vervet monkeys adapted their behaviour during a drought period by spending a greater proportion of time resting at the expense of feeding, moving, and social behaviour. As food availability decreased, vervet mortality increased. Peak mortality occurred when food availability was at its lowest and there was no standing water. A survival analysis revealed that higher fGCMs were associated with an increased probability of mortality. Our results suggest that with continued climate change, the increasing prevalence of drought will negatively affect vervet abundance and distribution in our population. Our study contributes to knowledge of the limits and scope of behavioural and physiological plasticity among vervet monkeys in the face of rapid environmental change.随着全球气候变化的影响日益凸显，动物物种将愈发受到极端气候及其对环境造成的连锁效应的冲击。目前亟需厘清动物对气候胁迫的生理与行为响应机制。本研究以反应范围模型（reactive scope model）为研究框架，针对南非境内2.5年间的干旱条件，探究其对黑长尾猴（Chlorocebus pygerythrus）的行为、生理应激及种群存活情况的影响。研究采集了气候、环境与行为相关变量数据，并通过粪便糖皮质激素代谢物（faecal glucocorticoid metabolites, fGCMs）指标来量化生理应激水平。 研究发现水源可获得性与资源丰度之间存在显著交互效应：当食物资源充足但无静止水源时，黑长尾猴的粪便糖皮质激素代谢物水平显著高于食物充足且存在静止水源的情境。干旱期间，黑长尾猴调整了自身行为策略，相较于觅食、移动与社交行为，它们将更多时间投入到休息活动中。随着食物可获得性下降，黑长尾猴的种群死亡率逐步升高，当食物可获得性降至最低且无静止水源时，死亡率达到峰值。生存分析结果显示，粪便糖皮质激素代谢物水平升高与个体死亡概率增加显著相关。 本研究结果表明，随着气候变化持续加剧，干旱事件愈发频发将对本次研究种群中的黑长尾猴的丰度与分布产生负面影响。本研究有助于深化对快速环境变化背景下，黑长尾猴行为与生理可塑性的极限与作用范围的科学认知。