Foraging behaviour of the root vole Microtus oeconomus in fragmented habitats

The effect of habitat fragmentation on spatial foraging behaviour in the ro ot vole Microtus oeconomus was investigated in seven experimental populatio ns. Four of the populations were established in large, continuous blocks (3 0 x 95 m) of meadow habitat (treatment plots), whereas the three remaining populations had six small rectangular habitat fragments (30 x 7.5 m) with v ariable inter-fragment distances (control plots). Both the small habitat fr agments and the large continuous habitat were embedded in a non-habitat mat rix area which was regularly mowed. Half-way through the study period, the continuous habitat in treatment plots was destroyed by mowing to give a con figuration identical to the control plots. Dyed bait placed at the edges an d in the interior of habitat fragments as well as in the matrix area was us ed to reveal differential use of these areas for foraging. Animals in the s mall-fragment plots fed more than expected along the edges, while edges wer e used according to availability in the large blacks of continuous habitat. In the fragmented plots, the frequency of foraging in the matrix decreased with increasing distance to the fragment border and with increasing inter- fragment distances. Furthermore, the frequency of use of more than one habi tat fragment in individual foraging ranges decreased with increasing inter- fragment distances. Reproductively inactive animals of both sexes fed more often along habitat edges than reproductively active animals. Reproductivel y active females fed exclusively in one habitat fragment, whereas inactive animals and especially reproductively active males frequently included more than one fragment in their foraging ranges. The only effect of habitat des truction was less foraging in the matrix habitat in the post-destruction tr eatment plots compared to the permanently fragmented control plots. This wa s probably an effect of different matrix quality. Root voles in these exper imental populations forage in edge and matrix habitat with great risk of be coming victims to predation, and the results are interpreted in this contex t.