食物蛋白质含量对高原鼠兔种群暴发的效应机理

Plateau pika is an herbivorous small animal which habitat in Qinghai-Tibet plateau area. It is also an original inhabitant in this area. In recent decades, population numbers have been sharply increasing with grassland degeneration, which is affecting livestock development and is exacerbating environment in this area. Thus, it is important to elucidate the mechanism of population outbreak of plateau pika for control this population. Some evidence showed that degraded grassland engendered an open environment in which pika lived well. However, population number still may be low when food was insufficient in the open environment, even if the degraded grassland offered a good environment with open visual for the pikas. In this project, we will answer a science question: what factor induces population outbreak in the process of grassland generation? We hypothesize that plant protein concentration is key factor to induce population outbreak of plateau pikas in Qinghai-Tibet plateau area. Firstly, we will test the constituents of food spectrum of the pikas, availability of food resource, protein concentration of food and population density in different phases of grassland generation, by which we want to explain the relationship between food protein concentration and food selection, availability of food resource and population numbers. Second, we will test the effects of protein concentration on reproduction at individual level and demographic parameters at population level by two methods: feeding young pikas in laboratory with different protein concentration food and supplying different protein food in enclosed populations. Our aims are to test and verify the hypothesis that we proposed and answer our science question in this project.

高原鼠兔是青藏高原特有的植食性哺乳动物。目前，随草地退化，其种群数量剧增，并制约区域生态环境及畜牧业发展。阐明高原鼠兔种群暴发机理，是认识并管理高原鼠兔种群的理论及实践依据。草地退化为鼠兔提供了开阔栖息地，但若缺乏生存与繁殖所必须的营养条件，动物种群数量依然会受到抑制。那么，草地退化过程中，引起高原鼠兔种群暴发的关键因子是什么？本项研究拟采用野外测定与调控实验相结合的方法，在高寒草甸不同退化草地，通过测定高原鼠兔食物谱、饲料可利用量及其蛋白质含量以及高原鼠兔种群数量，分析高原鼠兔食物选择与食物蛋白质含量及其资源量间的关系，阐明蛋白质含量对高原鼠兔种群数量的效应；通过室内饲喂和围栏添加不同蛋白质含量食物的调控实验，分析蛋白质含量对高原鼠兔个体生长和生殖发育及种群统计参数的机理效应，目的在于验证本项提出的食物蛋白质含量是引起高原鼠兔种群暴发的关键因子的假设。

高原鼠兔是青藏高原特有的植食性小型哺乳动物，也是青藏高原高寒草甸生态系统关键种之一。近几十年来，高原鼠兔的种群数量随草地退化而急剧增加，严重制约区域生态环境及畜牧业发展。退化草地为高原鼠兔提供了开阔的栖息环境降低了被捕食的风险，一直被认为是引起其种群暴发的主要原因。但若缺乏生存与繁殖必需的营养条件，动物的种群数量依然会被限制。因此，草地退化过程中，引起高原鼠兔种群暴发的关键因子是什么，目前尚不清楚。为了阐明高原鼠兔种群暴发的效应机理，本项目采用野外测定与调控实验相结合方法，在高寒草甸不同退化草地，通过测定高原鼠兔食物谱、食物可利用量及其蛋白质含量以及高原鼠兔种群数量，分析了高原鼠兔食物选择与蛋白质含量及其资源量间的关系；通过室内饲喂和野外自然样地中添加不同蛋白质含量食物的调控实验，分析了食物蛋白质含量对高原鼠兔个体生长和生殖发育及种群统计参数的效应机理。结果表明，高原鼠兔喜食食物中粗蛋白含量和粗脂肪含量显著高于不喜食食物，而粗纤维和碳水化合物含量则相反，食物选择指数与粗蛋白含量正相关；随着草地退化，植物的地上生物量虽然随草地退化显著降低，杂类草植物及高原鼠兔食物谱中的高蛋白质食物的相对生物量、胃内容物粗蛋白含量、体重和免疫功能显著增加，肠道寄生物的感染率及肝脏和肾脏指数显著下降，种群相对数量与高蛋白质食物的相对生物量显著正相关；室内饲喂高蛋白质食物，显著促进了高原鼠兔的生长发育、降低了粪便皮质醇的基础水平、增强了HPA轴的负反馈功能以及免疫和繁殖能力；野外添加高蛋白质食物显著增加了高原鼠兔的种群密度、种群补充率、存活率、免疫能力和种群繁殖能力。由此得出了草地退化为高原鼠兔提供了丰富的高蛋白质食物资源而引起其种群暴发的重要结论，该结论为认识并有效管理高原鼠兔种群提供了理论依据和实践基础。