Understanding differential and integral effects of climate and population density on vital rates e.g. survival, helps elucidate the ecological and demographic mechanisms underlying animal population dynamics.  The Mongolian gerbil (Meriones unguiculatus) is one of dominate rodents widely distributed in semi-arid, typical steppes, and desert grasslands in north of China.  We studied population dynamics of gerbils under semi-natural conditions using monthly capture–mark-recapture methods from October 2000 to 2004 in agro-pastoral ecotone of south-central Inner Mongolia, China. We used Cormack–Jolly–Seber (CJS) models to estimate apparent survival probability, and analyzed the difference of survival between males and females, or the survival seasonal variations.  Additionally, we used multistate （MS）models to test the difference of survival between adults with reproducing or reproduced strata and the sexually immature young.  Our results showed that the best approximating CJS model included the significant effect of full time（t）or season (month)- dependence on survival but not the effect of sex. These demonstrated that apparent survival probabilities displayed seasonal fluctuations of a lower apparent survival in summer compared to the rest of the year, and undistinguished survival between females( 0.788±0.013) and males (0.781±0.013）in the absence of limitation of environmental factors.  Our results also showed that the best and competition approximating MS model included age state (or stratum)-specific effect on apparent survival of

gerbils with a monthly (or seasonal) patterns. It may reflect the important life-history strategies adapting to the semi-arid or desert environment in Mongolian gerbils, Furthermore, there was evidence that population density negatively influenced survival with a time lag of 1 month in M. unguiculatus.  Considering the extrinsic environmental factors, increases in monthly total precipitation reduced the apparent survival of gerbils.  Moreover, these effects of population density-dependent and precipitation on the survival of female and male gerbils are different.  Therefore, we suggested that weather conditions may mainly mediate the change of habitable environment, supporting the optimum habitat hypothesis, and integrate density-dependent feedback to shape the different response of survival models between female and male gerbils.  These processes might construct an adaptive sexual-structure of population, and then affect the change of the other population parameters, consequently population growth rates. Pronounced a primary mechanism to regulate the small mammal’s population dynamic in northern high latitudes.

了解动物种群存活特征以及相关环境因子对其变化的独立或整合作用过程，有助于阐明动物种群动态的生态学机制。长爪沙鼠（Meriones unguiculatus）是分布于我国北方典型草原、荒漠草原及其毗邻的农牧交错带的优势鼠种之一。2000年10月至2004年10月通过标志重捕法研究了栖息于内蒙古农牧交错区草地生境的种群动态。本文通过MARK软件包中的CJS和MS模型分析了长爪沙鼠半自然围栏种群表观存活率（Φ，简称存活率）的性别（g）差异和年龄（as）特征表现及其季节变化格局，并对种群存活变化的密度和气候效应加以分析，旨在检验长爪沙鼠种群存活显示季节变化特征，并受密度制约和气候条件反馈调节的假设。结果发现，长爪沙鼠种群存活率初始最优模型Φ(t)p(g*t)中重捕时序（t）效应显著（ANODEV，F _27,47 =11.05，P <0.001），月季效应最优模型Φ(month)p(g*t)也显示存活率

季节变化明显（ANODEV，F _5,69 =31.69，P <0.001），总体呈现从春季到冬季经历下降再升高的“V”字型动态模式。在无环境因子限制条件下，雌鼠（0.788±0.013）和雄鼠（0.781±0.013）存活率差异不明显；存活率年龄差异表现明显的季节特征（ANODEV，F _5,246 = 67.85，P < 0.001），繁殖消耗在一定时期影响成年个体的存活。长爪沙鼠种群存活的季节格局反映其生活史对策中适应高纬度气候和食物等资源季节波动的重要特征。进一步统计发现种群存活率受密度制约、与降水负相关，其中密度制约效应具有一定的时滞，降水作用是即时的，上述效应的作用强度在雌、雄鼠的存活反应上有所差异。这些结果暗示密度制约整合水热条件介导最适栖息地环境变化，引发雌、雄鼠存活率差异性反应，进而影响其它种群参数变化，调节种群增长。这可能是北半球高纬度地区小哺乳动物种群调节的一个重要机制。