高寒草甸生态系统中高原鼠兔和高原鼢鼠的捕食风险及生存对策

调查青藏高原高寒草甸生态系统中两种主要啮齿动物及其天敌动物的种群密度，分析天敌动物对两种啮齿类的捕食方式、捕食强度，探讨啮齿类动物的捕食风险及生存对策。研究结果表明，高原鼠兔和高原鼢鼠的种群密度分别为4．97只／hm^2和10．6只／hm^2，而它们的主要天敌赤狐、艾虎和香鼬的种群密度分别为0．16只／100hm^2、0．37只／100hm^2、3只／100hm^2。艾虎和香鼬在取食过程中主要搜寻啮齿类的洞道系统，全部食物几乎都来源于洞道系统内；赤狐或取食地面活动的鼠兔，或挖掘洞口待高原鼢鼠封闭洞口时取食猎物。高原鼠兔在赤狐、艾虎和香鼬的食物中所出现的频次分别为100％、96．1％、100％，高原鼢鼠在3种天敌动物的食物中所出现的频次分别为87．5％、73．2％、0％。3种天敌动物对高原鼠兔和高原鼢鼠的捕食强度分别为0．703％和0．038％，高原鼠兔和高原鼢鼠所承受的捕食风险分别为0．780和0．393。高原鼠兔在高的捕食风险下通过行为对策和繁殖对策增加其适合度，而承受捕食风险较小的高原鼢鼠主要通过封闭的洞道系统和高的存活率增加其适合度。

The predation risks of the plateau pika and plateau zokor and their survival strategies in the Alpine Meadow Ecosystem

The present paper investigated the population densities and the survival strategies of plateau pika and plateau zokor,and the predation risks induced by their major natural enemies in the Alpine Meadow Ecosystem.The results showed that the population densities of the pika and the zokor were 4.97 ind./hm2 and 10.6 ind./hm2,respectively,while the densities of the natural enemies were 0.16 ind./100hm2 for red fox,0.37 ind./100hm2 for steppe polecat and 3.00ind./100hm2 for alpine weasel.We observed that the polecat and weasel mainly captured pika and zokor by searching the burrows,while the red fox hunted pika on the ground and captured zokor by digging the mounds.The examination of diet composition and feeding intensities showed that the pika constituted 100%,96.1% and 100% of the food of red fox,polecat and weasel,respectively,and the zokor constituted 87.5%,73.2% and 0%.The average feeding intensities of the natural enemies included 0.703% of pika and 0.038% of zokor and the predation risks of pika and zokor were 0.780 and 0.393,indicating that the pika has higher predation risk than zokor.The survival strategies of pika are to increase the fitness by unique behavior and reproductive rate,while the strategies of zokor are to enhance the fitness by sealing burrow system and survival rate.