关键词: 布氏田鼠, 生长指标, 主分量分析

Abstract: To the purpose of age estimation，15 growth indices in 560 specimens (males， 280; females，280)of brandt's vole (Microtus brandti)were studied by principal component annlysis(PCA)．The 15 growth indices are body weight，body length，tail length，greatest length of skull,basal length of skull，skull height,head back width，length of palatal bone，zygomatic width,interorbital width,nasal length,
width between maxillary incisor and molar，length of maxillary molar row ，length of mandibular molar row and dry wetght of Lenses．All analyzed indices were arranged on the first principal component axis (Z₁)which contribution rates are 74.0% (female) and 75.9% (male)．The results are as follows： 1．Interorbital width and tail length,as well skull height of female were regarded as poor growth indieators,because of their small projections on Z₁ .
2．Basal length of skull made the greatest projection on Z₁ ,so it reflected the growth best in both male and female.
3．Other growth indicators made projections above 0.829 and concentrated on Z₁ ．so they all can be used as age indicators of brandt's vole．
4 . Body weight and body length are the convenient indicators，but body length is not easy to measure accurately and body weight is affected by pregnent females．
5．Dry weight of eye lens not a suitable age indicator for brandt's vole,because the eye lens is so llght that the different between two age groups adjacent less than O.1mg．
6．Ahhough skull indices(except interorbital width and female's skull height)can all be used as age indicators, but they are not easy to obtain (except molar row and length between incisor and malar)．
Overall，the width between maxillary incisor and molar was used as the age indicator of brandt's vole based on both the results of PCA and practical circumstance．After further analysis,the population of brandt's vole can be divided into five age groups．It is the juvenile (1ength be tween maxillary incisor and molar is less than 6.49mm )， subadult (6.50— 7.33mm )，adultⅠ(7.34— 8.38mm) adultⅡ(8.39— 9.43mm)and old age group (over 9.44mm ).

Key words: Brandt's vole(Microtus brandti), Growth index：Principal component analysis(PCA)