东方田鼠种群扩散及活动对外部因子的反应格局

Effect patterns of external factors on dispersal and movement in reed vole populations

在野外围栏条件下,采用2×2×2析因实验,测定外部因子食物、捕食,以及同域分布物种黑线姬鼠的种间竞争对东方田鼠扩散和活动距离的独立作用及其交互作用的效应。研究结果表明,在所有的扩散个体中,幼体扩散的比例为71.0%。雄体扩散的比例为80.5%。东方田鼠扩散的趋势与其种群密度及补充量的变动一致。食物对扩散具有显著独立作用;捕食对扩散的作用接近显著;种间竞争对扩散的直接效应不显著;食物、捕食与种间竞争交互作用对扩散的效应亦不显著。在诱捕期内雄性的长距离活动比例及其诱捕期间长距离活动比例均显著大于诱捕期内雌性及其诱捕期间的长距离活动比例。不同处理种群间,仅雄体在诱捕期间的长距离活动比例具有显著差异;食物对雄体的长距离活动具有直接和间接(通过密度)的效应;而预防捕食者和竞争物种对不同处理种群雄体的长距离活动则无一致的效应。

We studied the independent and interacting effects of external factors such as food, predation and interspecific competition on the dispersal and moving distance of reed voles, Microtus fortis, using a 2×2×2 factorial experiment design under the field enclosure from March to December in 2001. The striped field mouse, Apodemus agrarius, a sympatric species of reed voles was regarded as a competitive species. Bird predators around the enclosures were observed and recorded every half an hour during the 24 hours after each trapping session. Kinds and numbers of mammal predators were estimated according to their trace or excrement. The minimum number of animals known to be alive was estimated as an index of population density using the calendar of capture method. Voles who had been captured more than once in removing areas in the enclosures were regarded as dispersers. Movement patterns were analyzed using the frequencies of short movement and long movement. The results showed that the proportion of juvenile voles was 71.0% and the proportion of male voles was 80.5% in all dispersers. Trends in the dispersal of the vole were consistent to the variance of population density and recruitment in the voles. The independent effects of food on the dispersal were significant, while those of predation were marginally significant. However the effects of interspecific competition on dispersal were insignificant. The interacting effects of food, predation and interspecific competition on the dispersal of the vole were not significant. The proportion of long distance movement in male voles was larger than that in the females during trapping sessions and between trapping sessions. There were significant differences of the proportion of long distance movement only in males between trapping sessions in different treatments. The effects of food on long distance movement were both direct and indirect (via density). Protection from predation and interspecific competition did not show a consistent effect.