中文摘要：

采用标志重捕法测定高原鼠兔家群年龄结构和性比，探讨其家群结构的季节变异及原因。结果显示，繁殖早期，家群由越冬成体和第1胎幼体构成；繁殖后期，家群主要由第1胎幼体构成。高原鼠兔家群年龄结构依季节存在显著的差异。5月，成体和雌性第1胎幼体个体数显著多于其他月份；5月和6月雄性第1胎幼体个体数显著多于7月和8月；6月第2胎幼体个体数显著多于7月和8月；7月雄性第2胎幼体个体数显著多于8月。7月和8月，第1胎幼体个体数显著多于第2胎幼体。高原鼠兔家群内5月成体性比显著高于7月和8月。结果表明，高原鼠兔在冬季漫长、食物匮乏以及繁殖季节极短等条件下，调整家群结构，提高繁殖成功率，使其种群在严酷的高寒环境中得以延续。

英文摘要：

From May to August of 2005 and 2006, the age structure and sex ratio within family groups of plateau pikas （ Ochotona curzoniae ） were studied in Maqin County, Qinghai Province, by mark-recapture method. The result indicated that in May the family groups were composed of adults and first-litters （male： Adult, 47% ; Juvenile, 53% ; female： Aduh, 40% ; Juvenile, 60% ） , and in August were mainly composed of first-litters （ male, 58% ; female, 51% ）. Composition of plateau pika families averaged 5.1 adults （2.4 males and 2. 7 females） and 13.0 juveniles （5.2 males and 7.8 females ） that survived long enough to be caught. There were significant differences in age structure within family groups among different months. Individuals of adults and female first-litters in May were significantly larger than those in other months. Individuals of male first-litters in May and June were significantly larger than those in July and August. Individuals of second-litters in June were significantly larger than those in July and August; individuals of male second-litters in July were significantly larger than those in August. Individuals of first-litters in August were significantly larger than those of second-litters. The result also showed that these was no significant difference from 1：1 in sex ratio during whole breeding season, whereas sex ratio of adult in May was significantly higher than that in July and August. It is suggested that plateau pikas living in environmental conditions where it have a long winter time, short breeding seasons, rigorous climate and limited food supply adjust their family group structure to improve reproductive success.