洞庭湖区东方田鼠迁移的研究

洞庭湖区东方田鼠以湖滩上的芦苇＋荻或薹草沼泽为最适栖息地，枯水季节，多在其上生长、繁殖。汛期，随着湖水上涨，湖滩面积缩小，东方田鼠在拥挤的的压力下或直接被洪水所迫，越过防洪堤迁入垸内。东方田鼠在湖滩及农田间的迁移主要取决于湖水水位及种群密度，无固定的迁移时间。迁入垸内的东方田鼠主要分布于靠近防洪堤一带，其捕获率随着与防洪堤距离的增加而递减。个体较大的东方田鼠迁移距离较远。在迁移期，迁入垸内的东方田鼠的性比在不同的距离上无显著差异。湖水回落时，东方田鼠随湖滩出露而迁回沼泽草地。回迁时，个体较大的雄性首先回迁的比例较高。迁入垸内的东方田鼠，栖息在荒坡地的种群密度大于在农田中的种群密度；东方田鼠不在农田越冬，小部分可在岗地荒坡中越冬，但少有增殖。按迁移动因看，此种迁移乃洪水逼迫所至，而由逼迫外迁和自动回迁构成循环，保证了种群对湖区特殊环境的适应。

STUDIES ON THE MIGRATION OF MICROTUS FORTIS IN DONGTING LAKE AREA

Microtus fortis lives on the beach of Dongting Lake from autumn to spring when the water level of the lake is low. As the rising of the water level of the lake in spring or in early summer, and the area of the lake beach becoming narrow, M. fortis crosses the dike and migrates to the farmland under the pressure of overcrowd or being forced by the flood directly. When M. fortis started to migrate depended on the water level of the lake and the population density. M. fortis often causes serious damages on crops when it moves to the farmland. When M. fortis crossed the dike, it distributed on the farmland and the uncultivated land. The adults moved longer distance than the youngs did. There were no differences between sexes on the dispersal distances. The voles were mainly distributed within the area of the farmland or uncultivated land 5 km from the dike during summer. The rate of capture declined as the distance from the dike increased. The rate of capture on uncultivated land was higher than that on farmland. When the lake beach emerged in autumn, the voles moved back. The ratio of males among the dispersals was high when the voles started to move back in autumn.