【摘要】 <正> 在国家的社会主义建设中,动物生态学的主要任务不外是改造有益有害动物的种群,增加有益动物的数量,减少或消灭有害动物的数量,使之更符合于国民经济的需要。啮齿动物对农、林、畜牧、保健各项事业的危害甚大,故在“农业发展纲要(草案)”上的除四害一项中规定要消灭它。而在与鼠类的斗争中就需要掌握其种群状态、数量变化的规律等等,以求预测鼠害的发生,及时采取各项灭鼠的措施。在种群研究中年龄问题是十分重要的,了解其年龄组成可以知道其种群是否健康、繁殖情况、及其数量的发展趋势。红背(鼠平)(Clethrionomys rutilus)为东北林区的害鼠(寿振黄等,1958)。所以我们就以此鼠为材料,来研究这项既有实践意义又有理论价值的问题。更多还原

【Abstract】 The material used for this study was collected from Dailing, Lesser Khingan Mountains, in Northeastern China, from 1956 to 1957. A total of 863 skulls of both sexes were soaked in hot water, and then carefully cleaned. The first molar of the lower jaw was chosen for microscopic examination, and the length of its roots or branches measured by a micrometer.Based upon the morphology of the tooth roots, four age groups have been devised. The first group, with the lower end of its molar root undivided, are considered as juveniles; the second group, with the lower end of its molar root divided into two branches measuring less than 0.7mm in length, as subadults; the third group, with a root branch measuring 0.7-1.7mm, as adults; and the fourth group, with root branch, meassuring more than 1.7mm, as old adults.The body weight of this vole shows a considerable range of variation, and there exists no exact relationship jbetween the age groups and their body weight. Most probably, individuals of the first year weigh less than 20 gms, while those of the second year have a body weight of more than 20 gms.The first group or the so-called juveniles, about 2 or 21/2 months old, are sexually inactive. The three other groups, subadults, adults, and old adults, have the power of reproduction.Seasonal variations in population composition have been observed. In spring and summer, subadults and adults are dominant individuals. After July, however, juveniles are more numerous than subadults and adults.更多还原