The role of habitat barriers in woodlot recolonization by small mammals

The immigration and colonization of small mammals into a small depopulated wooded area surrounded by meadows was monitored by live-trapping and then compared with the same processes in an open forest following removal trapping. Rate of recolonization was lower in the depopulated woods than in the continuous forest. Bank voles, Clethrionomys glareolus , predominated the small mammal communities before removal; however, after removal the percentage of bank voles decreased and species diversity increased. When comparing the bank voles from the wooded area with the continuous forest, we found a higher percentage of sexually active animals, the lack of reproducing females and slightly lower body weights. Based on these characteristics the bank voles that recolonized the small woods were regarded as dispersers. The meadow belt surrounding the depopulated wood acted as a "filter" which stopped some bank voles and allowed others to pass through, and also "selected" different species crossing it according to their mobility. Some effects of such habitat barriers on the functioning of metapopulations are discussed.