布氏田鼠种群生理年龄结构的研究

本文根据胴体重分布将布氏田鼠划分为越冬鼠与当年鼠两组,然后再根据生理学指标将当年鼠划分为性成熟鼠(成年)和性未成熟鼠(幼年)。由于生理年龄与时间年龄不一致,故本文并不强调各种形态指标来划分时间年龄组。5月下半月以前种群主体为越冬鼠,但在当年鼠出现地表面后,当年鼠取代越冬鼠成为种群主体,到7月下半月越冬鼠已降到10％以下。当年生的幼鼠春季生长发育旺盛,很快成为当年成鼠。晚夏和秋季出生的个体当年性不发育成熟。秋季种群主体为当年幼鼠。越冬鼠和大部分当年成鼠从种群中消失。比较种群数量上升与下降年份,春季越冬鼠胴体重的轻重与第一批当年鼠(K_1)出现规模可能是种群数量升降的重要指标。

STUDY ON PHYSIOLOGICAL AGE STRUCTURE OF BRANDT' s VOLES(MICROTUS BRANDTI)

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 various 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 the voles born of this year appeared on surface in late half of May, they took place of overwinterings rapidly and in late half of July the percentage of over wintering had declined to less than 10%. The voles born in spring grew and maturated rapidly and became the sexmaturatings to reproduce. But the voles born of late Summer and Autumn grew and maturated slowly and did not reach sex-maturating in fall. The overwinterings and most of the sex-maturating voles disappeared from population in fall and the main part of population was the sex-non-maturating voles. It is found that the mean net body mass of overwinterings in spring and the appearing scale of the first cohort may be important indexes to predicting population increasing or decreasing by compared the population-increasing-year with population-declining-year.