Survival, Immigration and Habitat Quality in the Mediterranean Pine Vole

Abstract

There is evidence that the Mediterranean pine vole does not display population cycles as some microtines do. The aim of our study was to test whether dispersal between populations could be a stabilizing factor of densities of this species. Four populations were studied by capture-recapture in southern France. Two habitats of different quality were sampled. Probabilistic estimators were used to estimate population sizes, survival rates, recruitment and immigration. Densities were similar in all populations but some variations were obvious and not related to habitat quality. Survival was constant throughout the seasons in the high-quality habitat, but not in the low-quality habitat where it decreased critically during spring. Recruitment was low in the former habitat, and almost did not occur in the latter. Immigration was strongly correlated to population size changes and was the factor causing the variations observed between patches of high quality. Immigration allowed the persistence of the population in the patch of low quality at densities similar to the others. A source-sink metapopulation dynamics was inferred from these results. The existence of adaptive dispersal is discussed as a stabilizing factor of population densities in the Mediterranean pine vole. The adaptiveness of dispersal is conditioned by the existence of discontinuous distribution and heterogeneity in population dynamics caused by different habitat quality or variable immigration patterns. The generality of this stabilizing mechanism is discussed in microtine populations.