Voles in basement
My folks thought they were having a problem with mice in their basement so they put out sticky traps with peanut butter. Turns out the problem is voles, not mice. They actually saw one run around the perimeter of the basement and out between a couple of the rocks of our foundation (foundation is over 100 years old, stacked stone in most places with a dirt floor, not concrete or cinder block). They filled the hole with spray foam and have since started trying to fill other potential entry spots, but we think the voles are getting too smart. They have set out additional sticky traps and the critters escaped with the peanut butter (they actually pushed loose rocks onto one of the traps to get at the PB and might have been dusty enough not to get stuck in the glue on the second).
Any thoughts on a different way to get rid of the voles? Any ideas on other things that could be done to keep the voles from getting in in the first place? (Please don't advise getting a cat. It is really not an option for them.) Thanks!