关键词: 布氏田鼠, 时间年龄, 生理年龄, 性成熟鼠 性未成熟鼠, 胴体重

Abstract: According to the distribution of net body masses (the body mass excluding abdominal viscera)， Brandt's voles are divided into two groups，overwintering voles and voles born of this year．Because the vole's physiological age differs from the chronological age． it is not necessary to divide the chronological age groups by using varions morphological indexes such as body mass．body length,net body mass，morphology of skull and tooth etc．The voles born of this year are divided into sex-maturating (adult) and SeX—non—maturating voles(juvenile)on the basis of physiological indexes．The main part of population was overwinterings before late half of May．When thevoles born of this year appeared on surface in late half of May，they took place ofoverwinterings rapidly and in late half of July the percentage of over wintering haddeclined to less than 10%．The votes born in spring grew and maturated rapidly andbecame the sexmaturatings to reproduce．But the voles born of late Summer and Atumn grew and maturated slowly and did not reach Sex—maturating in fall. The overwinterings and most of the sex—maturating voles disappeared from populationinfallandthe main part of population was the sex—non maturating voles.It is foundthat the mean net body mass of overwinterings in spring and the appearing scale ofthe first cohort may be important indexes to predicting population increasing or deareasing by compared the population-increasing-year with population-declining-year.

Key words: Brandt's voles, Chronological age, Physiological age, Sex-maturating volesl Sex—nori—maturating voles, Sex-non-maturating voles, Net body mass(the body mass excluding abdominal visera)