Age structure of Mus musculus population

457 samples of Mus musculus were divided into four age groups according to the body weight and reproductive characters. They were the young group(Ⅰ,less than 80g),subadult group(Ⅱ,81-140g),adult group(Ⅲ,141-200g)and older group(Ⅳ,more than 200g).The results showed that there was a significant difference among four age groups in the reproductive capacity,and the reproductive capacity increased with the population age increment.