You could also try planting certain plants that repel rodents around your trees and garden beds, like Daffodils, Crown Imperials, etc. Not sure exactly how much of an effect these will actually have…but at the very least, you will have a much prettier yard!
The mole kingsnake (Lampropeltis rhombomaculata or occipitolineata) will also follow through vole tunnels to catch voles. But, they are hard enough just to find out in the wild (due to being underground most of the time), much less in any retail stores, lol…