Effects of predation on temporary autumn populations of subadult Clethrionomys glareolus in forest clearings

Using netting to exclude both avian and mammalian predators in a field expe riment we investigated the effect of predation and predation risk on surviv al, body weight development and microhabitat preferences of temporary, suba dult Clethrionomys glareolus populations in two forest clearings during the autumn of 1996. Female bank voles were found to be influenced to a higher degree than males. Female survival was higher on predator-excluded grids co mpared to predated grids, whereas there was no clear response in males Fema les also gained more weight on predator-excluded grids compared to both mal es on the same grids and females on predated grids. There was no clear trea tment effect when mean body weights were compared in each trapping period. However, mean female body weights on predator-excluded grids were significa ntly higher in November than in September. This was not the case on predate d grids. There was a clear treatment effect on female microhabitat preferences On pr edated grids female bank voles were captured at trap stations with more cov er than females on net grids. A similar but less clear tendency was seen in males. On both net grids in both September and November female bank voles were trapped at trap stations with less cover than males, whereas the oppos ite was true for both predated grids in both months.