高寒草甸生态系统中高原鼠兔的繁殖特征

2002年4月至8月，在中国科学院海北高寒草甸生态系统定位站附近，采用标志重捕法对高原鼠免的繁殖特征进行了研究。高原鼠兔的繁殖具有明显的季节性差异，4月下旬和5月为繁殖高峰期，雄性的睾丸重而饱满，雌性的怀孕率最大。雄性成体的体重和睾丸重在繁殖期的不同时段具有显的差异，在4月11日至5月10日、6月11日至7月10日体重和睾丸重之间呈显正相关。雌性怀孕早期胚胎数与临产前胚胎数没有显差异，未发现胚胎吸收现象；同时，胚胎数在繁殖期的不同时段存在显差异。采用种群统计学中同生群的划分方法，将5～8月份出生的幼体依次记为L1、L2、L3、L4。在出生后20天内L1、L2幼体存活率明显高于L3、L4；在从出生50天至80天期间L4的存活率显高于L2。当年出生的雌雄幼体在发育上存在不同步现象，当年出生的雌性幼体性成熟早，有的可以直接参加繁殖，但当年出生的雄性幼体却无此现象。结果表明：在海北地区，经过综合治理后，高原鼠兔的生境发生改变，其繁殖策略也随之发生改变，即，减少每次繁殖活动的投入，增加繁殖次数，延长繁殖时间。

Population Reproductive Characteristics of Plateau Pika in Alpine Meadow Ecosystem

From April to August of 2002, the population reproductive ecology of plateau pikas (Ochotona curzoniae) were studied in the Haibei Research Station of Alpine Meadow Ecosystem by mark-recapture method. The reproduction of the plateau pika had significant difference in different reproductive periods. From late of April to May, it was the breeding peak of pika, at that time, the testis weight and the rate of gestation are the biggest. The body weight and testis weights of male adult also had apparent difference in different reproductive periods. There was a positive correlations between body weight and testis weights during 11 April to 10 May and 11 June to 10 July. The litter size had apparent difference in different reproductive time. But the litter size had no apparent difference in early stage of pregnancy and parturient stage. The young pikas which were borned from May to August were marked as L_1 , L_2 , L_3 , L_4 by the method of cohort. The survival rates of L_1 and L_2 were much higher than that of L_3 and L_4 at 20 days after birth. The survival rate of L_1 was evident higher than that of L_2 at 80 days after birth. The growth of different gender young pikas were not synchronization maturation. The young female pikas were developing faster than young male pikas in sexual maturation. So some young female pikas could take part in reproductive activity directly but young male could not. These results indicated that the reproductive strategy of plateau pikas had changed with the habitats in Haibei area. The plateau pika had decreased the investment of every reproductive activity, increased the times of reproductive activity and extended the reproductive period.