For voles, I have tried different traps and poisons but the most effective has been the 'The Giant Destroyer' rodent control gas sticks available from RONA:
"Sticks for rodent control "Giant Destroyer" in packs of 4. This product has been used successfully for many years to control rodents such as moles, marmots, rats, skunks and squirrels. The Giant Destroyer does not harm lawns, plants or trees and easily penetrates to the bottom of tunnels and burrows."
https://www.rona.ca/en/rodent-contro...k-of-4-5067001
You basically find a good sized hole at an obvious entrance/exit for the critters, light the fuse, shove the stick in the hole and once burning, cover the hole. Quick and very effective. You'll know if you didn't get them all if the 'hole' re-appears nearby in a few days.