关键词: 长爪沙鼠, 种群特征, 繁殖, 适应

Abstract: This paper deals with two gerbil (Meriones unguiculatus) populations from the sites of the farmland and the grassland in Siziwang Banner north to Yin Mountains,Inner Mongolia. 243 gerbils were obtained from the farmland population and 271 from the grassland population in June, then 222 and 185 in September, respectively. The distance from one site to the other is about sixty km. and there is no topographic difference between them. Population densities in the two sites are similar.In summer (June) the body length and the body weight in all age classes of the grassland population were higher than that of the farmland population, and in autumn (September) there were no significant differences between them. It meant that from summer to autumn the growth of the gerbils in the farmland was greater than that in the grassland. In autumn the percentage of the pregnant females, the percentage of the males with enlarged seminal vesical and the testis length of the adult in the farmland were bigger than those in the grassland, respectively, and there were no significant differences in these parameters between the two populations in summer. The litter size in the grassland population was higher than that in the farmland population in summer and no significant difference was found in autumn. There was significant difference in age structure between the two populatons in autumn, the juvenile and subadult occupied 58.10% in the farmland population, while only 13.52% in the grassland populatiou and the age structure of the two populations was rather similar in summer. It meant that the reproductive intensity of the farmland population decreased slowly from summer to autumn wheras the reproductive intensity of the grassland population decreased quickly. The planting of crops provided the gerbil population in the farmland with a favourable supply of food from summer to autumn while the ploughing after harvest made the farmland an unfavourable place for living and food from winter to spring. In the grassland which was seldom disturbed by human activities the living condition of the gerbil was more stable than that in the farmland.This resulted in the differences in the adaptive characteristics between the two populations.

Key words: Mongolian gerbil, Meriones unguiculatus, Population characteristics, Reproduction, Adaptation