SURVIVAL, IMMIGRATION AND HABITAT QUALITY IN THE MEDITERRANEAN PINE VOLE

1. 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 fact or of densities of this species. 2. Four populations were studied by c apture-recapture in southern France. Two habitats of different quality were sampled. Probabilistic estimators were used to estimate populati on sizes, survival rates, recruitment and immigration. 3. Densities we re similar in all populations but some variations were obvious and not related to habitat quality. 4. Survival was constant throughout the s easons in the high-quality habitat, but not in the low-quality habitat where it decreased critically during spring. Recruitment was low in t he former habitat, and almost did not occur in the latter. 5. Immigrat ion was strongly correlated to population size changes and was the fac tor causing the variations observed between patches of high quality. I mmigration allowed the persistence of the population in the patch of l ow quality at densities similar to the others. A source-sink metapopul ation dynamics was inferred from these results. 6. The existence of ad aptive dispersal is discussed as a stabilizing factor of population de nsities in the Mediterranean pine vole. The adaptiveness of dispersal is conditioned by the existence of discontinuous distribution and hete rogeneity in population dynamics caused by different habitat quality o r variable immigration patterns. The generality of this stabilizing me chanism is discussed in microtine populations.