Abstract: Relative fatness is an important general indicator of physiological body condition of small mammals and reflects their adaptive ability to the environment. The relative fatness of Mongolian gerbils ( Meriones unguiculatus) was studied from March to November 1997 in TaiPuSi Banner, Inner Mongolian in China. It was calculated by the formula : K′= 100W_N/L³ (g/cm³ ), where L indicated the naso-anal length , and W_N was the carcass body weight minus all internal organs. The removal of all internal organs is to exclude the possible ones caused by the weight of food in digestive canal , embryos or pregnancy and sexual organs. Results indicated that the relative fatness changed significantly with age which relative fatness of sub-adult individuals was significantly higher than that of adult ones. Its seasonal changes of different sexual age groups were in accordance with this rule : relative fatness of rodents becomes high in spring , lowest in summer and fatted again in autumn in high altitude zones. Our results indicated that the relative fatness of the female was higher than that of the male before August ; and the relative fatness of the sub-adult and adult male groups were fatted until September or October , while that of the female group fatted until November. Combined with the life-history characteristics , it was concluded that Mongolian gerbils adjusted its hysiological conditions to adapt to the environment in different life stages. In addition , the monthly relative fatness in males negatively correlated to its monthly population relative size , and relative fatness in the adults had a significant positive correlation with the population size 4-month later. Our results indicated that using relative fatness as an indicator in forecasting relative size of population in Mongolian gerbils has its reference value.

Key words: Mongolian gerbil (Meriones unguiculatus), Carcass body mass, Relative fatness, Age, Season

摘要： 采用胴体重(去除内脏的体重, 记为W_N ,) 替代传统计算公式中的体重(W) 建立肥满度指标K′= 100 W_N/L³ (g/cm³ ) 对长爪沙鼠肥满度的年龄和季节变化特征进行研究。结果显示: 该鼠肥满度年龄组间差异显著, 未成年个体的肥满度明显高于成年个体; 各性别年龄组肥满度季节变化明显, 趋势基本一致, 春季高、夏季最低、秋季又行育肥。在春夏季繁殖期(8 月以前), 雌鼠的肥满度大于雄鼠。成年雌鼠秋季育肥时间晚于其他个体组。长爪沙鼠肥满度的年龄差异和季节变化反映了该鼠在不同生活时期对环境的生理适应特征和对策。此外, 各月肥满度与当月及其后第4 个月的夹捕率存在一定的相关关系, 提示该指标在短期预测长爪沙鼠种群数量方面可能有其参考价值。

关键词: 长爪沙鼠, 胴体重, 肥满度, 年龄, 季节