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根据胴体重的频次分布和每５ｇ胴体重组的鼠所对应的发育与繁殖状况，将黄胸鼠分为５个年龄组：Ⅰ．幼年组：胴体重≤３５ｇ；Ⅱ．亚成年组：３６～６５ｇ；Ⅲ．成年一组：６６～１００ｇ；Ⅳ．成年二组：１０１～１３５ｇ；Ⅴ．老年组：＞１３５ｇ。经ｔ检验，各组间的胴体重、体重、体长、尾长都有显著性的差异。各年龄组间的体重与胴体重存在显著的正相关，前３个年龄组的体长和尾长与胴体重之间有极显著相关性。各年龄组的雌性比变化不大，雌鼠的怀孕率和繁殖指数在前４个年龄组随着年龄的增大而增加，在成年二组达到最高，到老年组则明显降低，参产雌鼠由幼年组的０％逐渐增加至老年组的１００％。雄鼠的睾丸随着年龄的增长而增大，但老年组增加幅度不明显，下位率则由０逐渐增加到１００％。每年１～４月种群中以成年一组和成年二组为主，随后，幼年组和亚成年组的比例增加，在７～１２月各年龄组则保持着一定的平衡状态。
According to the frequency distribution of carcass weight and the developmental and reproductive status of the mice per 5g carcass recombination, the rats were divided into five age groups: Ⅰ. Juvenile group: carcass weight ≤ 35g; Ⅱ. Sub-adult group: 36 ~ 65g; Ⅲ. Adult group: 66 ~ 100g; Ⅳ. Adult two groups: 101 ~ 135g; Ⅴ. Elderly group:> 135g. After t test, the carcass weight, body weight, body length, tail length between the groups have significant differences. There was a significant positive correlation between body weight and carcass weight among all age groups. The body length, tail length and carcass weight of the first three age groups were significantly correlated. Females in each age group had little change, the pregnancy rate and reproductive index of females increased with age in the first 4 age groups, reached the highest in the second group and decreased significantly in the older group Rats gradually increased from 0% in juvenile group to 100% in geriatric group. The testis of male rats increased with age, but the increase rate of the elderly group was not obvious, and the rate of the lower one gradually increased from 0 to 100%. From January to April each year, the adult group and the adult group were the main groups. Afterwards, the proportion of juvenile group and sub-adult group increased, and the balance between July and December was maintained in all age groups.