自然和人为胁迫下普氏原羚种群动态调节机理研究

Studies have shown that predators can regulate prey's population dynamics through not only direct predation, but also indirect predation risk effect which can influence the prey's behavioural and physiological responses. There have been increasing interests in studying predation risk effects on prey's population dynamics in recent years. Przewalski's gazelle is an endemic species to China which ranges freely on the grassland around Qinghai Lake area under both natural and anthropogenic threats. Its population size has increased slightly during the past 20 years due to great conservation efforts, but its total polulation size is still very small with a conservation status being classified as endangered species. Understanding the mechanisms and reasons for its population dynamics is critical for conservation of this species. This project will be conducted with subpopulations at two distribution areas with different conditions of natural and anthropogenic threats. A series of field data will be collected, inclduing population parameters of the gazelle and its main predator (wolf), behavioural data of the gazelle udner different environmental conditions, and fecal samples of both the gazelle and the predator. The contents of cortisol (the stress hormone) will be measured at the laboratory from the gazelle’s freshly-frozen fecal samples as an indicator of overall level of its response to stress from both predator and anthropogenic threats. The project will examine the direct predation effects on the gazelle from the wolves, and the indirect predation risk effects from both the wolves and the anthropogenic threats. Two hypotheses regarding predation risk effects, i.e., the predation stress hypothesis and the predator-sensitive foraging hypothesis, will be tested with the behavioural data, population dynamic data, and physiological data of the gazelle. We aim to elaborate the relationship between the gazelle’s population dynamics and the gazelle’s behavioural and physiological responses to both its predator and anthropogenic threats in order to better understand the mechanisms underlying the gazelle’s population dynamics in different areas. This study will also identify the main threats to the gazelle populations in different areas, which will be necessary for development and implementation of site-specific and scientific conservation measures and action plans for the gazelle. Thus, this study will have strong implications for both the theory on predator-prey interactions and conservation practice.

捕食者不但可通过直接捕食控制猎物数量，还可通过捕食风险效应影响猎物行为和生理而间接影响其繁殖和种群动态，因此研究捕食风险效应对猎物野外种群动态的影响日益受到关注。普氏原羚是我国特有种，生活在青海湖周边受天敌捕食和人为胁迫严重影响的草原上，其种群数量在过去二十年虽有缓慢上升，但仍处濒危状态，探明其中原因是保护该物种的关键前提。本课题拟对二个面临不同人为和自然胁迫压力的普氏原羚亚种群进行比较研究，利用野外行为生态观察和实验室生理分析（应激激素浓度）相结合的方法，明晰捕食者对普氏原羚的直接捕食作用、及捕食和人为胁迫的捕食风险效应，检验捕食风险效应的两个假说（捕食应激假说和捕食者敏感取食假说），从生理和行为两个角度来阐释普氏原羚种群动态的影响因子和调控机理，加深对捕食者—被捕食者关系的理解；甄别不同分布小区普氏原羚种群所受的主要威胁，为制定有针对性的保护措施、恢复该濒危物种提供科学依据和指导。

该项目对普氏原羚的一个圈养种群和两个野外种群进行了比较研究，测定了粪样中皮质醇激素浓度，分析了不同环境压力下的原羚的应激反应行为、皮质醇浓度变化、应激反应行为与皮质醇浓度的关系等，以期从行为和生理反应两个角度揭示环境压力对普氏原羚个体行为生态、生理、种群动态的影响机理。研究结果表明：1）普氏原羚粪样皮质醇在-20℃的温度下保存稳定性可达至少50天，这一结果解决了野外保存、运输粪样的难题，也为其它类似物种相关研究的粪样保存提供了参考。2）通过检测普氏原羚粪样中类固醇性激素、尤其是孕酮的含量，可以有效地鉴别粪样的性别属性，这可以为野外难以分辨动物个体情况下判别粪便的性别属性提供了可能。3）圈养种群原羚的粪样皮质醇浓度及警戒行为强度在产羔期最高，这意味着产羔期的雌性原羚面临的捕食风险效应最大，而这些反应对其繁殖和种群调节可能带来不利影响，因此需避免给产羔期的雌性带来额外的捕食风险。4）两个野外种群的雌性原羚粪便皮质醇在产羔期最高，并存在显著的地域性差异，这种地域性差异可能反映了两个不同地域种群所面临的捕食风险压力的差别；但是，两个野外种群的警戒行为频率在交配期最大，这可能说明原羚在面对长期的捕食风险胁迫时，警戒频率的提高更有利于发现和逃避潜在的捕食风险。5）普氏原羚及同域分布的藏原羚和藏系绵羊的肠道菌群存在相似的趋势，具有脊椎动物肠道菌群组成的共同特征，这可能是由于在同一生境共享同样的食物资源而造成的。6）普氏原羚种群数量近年来保持稳定增加的趋势，2016、2017和2018年的种群数量分别为1369、1275和2057只，其种群数量与生境植被生物量显著正相关。.项目组成员参加了两次国际和两次国内学术研讨会，并做分论坛报告或墙报展示；发表SCI期刊论文3篇，中文核心期刊论文1篇；该项目进展较顺利，培养了人才，较好地完成了各项原定计划和目标。