Rob,
Voles are suckers for pit traps. I did a research project in College that involved finding the little trails the voles leave in the grass, digging a hole across the trail and placing a large coffee can in it with the top at ground level. We put bait in it - rolled oats maybe? (I bet hamster food would be enticing). Of course, we just marked the vole (or shrew), released them and kept stats for the class report. If you get any shrews - keep them alive - they eat insects and other bugs. Happy hunting.
