关键词: 东方田鼠, 黑线姬鼠, 繁殖特性, 退田还湖, 洞庭湖区

Abstract: The reproductive characteristics of the striped field mouse (Apodemus agrarius)and the Yangtze vole (Microtus fortis)were studied in an area being restored to lake in the Dongting Lake region. There were two main ways that farmland was restored. In Double Restoration Polders (DRP)both human habitation and agricultural activity were removed,while in Single Restoration Polders (SRP)only human habitations were removed but agricultural activities continued. The study was conducted in January,April,July and October from 2003 to 2006. Snap traps were used to get samples in all plots throughout
the census. Seven typical plots (seven different types of habitats for small mammals)were selected for investigation.Habitat 1 was hilly woodland around the lake which was covered by some shrub,arbor and herb,and M . fortis often immigrated to here from beach of lake during flood season. Habitat 2 and habitat 3 were normal farmland in protected polders. There was an M. fortis population migrating into habitat 3 during flood season,as there was a large stretch of beach outside of the dike near the habitat. Habitats 4 and 5 were SRP. Habitat 4 was still farm and the majority of the area of habitat 5 was planted in one kind of poplar (Populus spp. ). Habitat 6 was typical DRP,which was also covered by arbor. Habitat 7 was the beach of lake which has fully developed (matured beach),it was covered by Carex spp. and Polygonum hydropiper. The reproductive characteristics of Apodemus agrarius and Microtus fortis were compared among these habitats, and also compared with historical data we acquired during 1980 and 1990. The indices of reproduction of females were higher than those in the historical data for both A. agrarius,which was the dominant species in farmland,and for M. fortis, which was dominant species on beach of the lake. Both species were at a low point of multi-annual population fluctuations. Both species displayed no significant changes except for in DRP during the summer. In normal situations,the populations on the matured beach were forced to cross the dike and immigrate into the farmland or hillock when the beach was covered by water in flood season. However,there were some higher points and some abandoned dike in DRP which may not be covered by water and may became refugia for Microtus fortis and Apodemus agrarius. As a result,they did not across the dike,
but rather,just moved to the high level places. The population of the Microtus fortis which still stayed in DRP during summer (flood season)continued their reproductive peak,and the index of reproduction was 1.54 (I♀ =3. 36),whereas the population of M . fortis which was forced to migrate into farmland or hillocks almost stopped breeding and its fecundity became low. We expected that the Microtus fortis which didn’t undergo long distance migration would remain highly fecund in summer. On the other hand,Apodemus agrarius showed opposite responses in terms of reproduction. The historical data
showed that there were two breeding peaks in a year,the first peak was in spring and the other was in autumn. Although there was a relative decrease in summer,there still was some reproduction. However,the Apodemus agrarius in DRP almost stop breeding in the summer after migration from low level places to high level places,and the index of reproduction was only 0.03 (I♀ = 0.05). In addition to migration,competition between Microtus fortis and Apodemus agrarius in DRP might contribute to the drastic decrease in reproduction for Apodemus agrarius. The same phenomenon was found in the historical data from 1990. This study has shown different responses of A. agrarius and M. fortis in reproduction after migration in DRP in summer.

Key words: Dongting Lake region, Reproduction characteristics, Return the cropland back into lake, Striped field mouse (Apodemus agrarius), Yangtze voles (Microtus fortis)