Demography and population dynamics of the mouse opossum (Thylamys elegans)in semi-arid Chile: seasonality, feedback structure and climate

Here, we present, to the authors' knowledge for the very first time for a s mall marsupial, a thorough analysis of the demography and population dynami cs of the mouse opossum (Thylamys elegans) in western South America. We tes t the relative importance of feedback structure and climatic factors (rainf all and the Southern Oscillation Index) in explaining the temporal variatio n in the demography of the mouse opossum. The demographic information was i ncorporated into a stage-structured population dynamics model and the model 's predictions were compared with observed patterns. The mouse opossum's ca pture rates showed seasonal (within-year) and between-year variability, wit h individuals having higher capture rates during late summer and autumn and lower capture rates during winter and spring. There was also a strong betw een-year effect on capture probabilities. The reproductive (the fraction of reproductively active individuals) and recruitment rates showed a clear se asonal and a between-year pattern of variation with the peak of reproductiv e activity occuring during winter and early spring. In addition, the fracti on of reproductive individuals was positively related to annual rainfall, w hile population density and annual rainfall positively influenced the recru itment rate. The survival rates were negatively related to annual rainfall. The average finite population growth rate during the study period was esti mated to be 1.011 +/- 0.0019 from capture-recapture estimates. While the an nual growth rate estimated from the seasonal linear matrix models was 1.026 , the subadult and adult survival and maturation rates represent between 54 % (winter) and 81% (summer) of the impact on the annual growth rate.