Hi, Well on 4 acres there's no easy answer here. First, you must figure out which creature you have making the trouble. Moles generallly make raised ridges in lawns where they tunnel underneath to eat earthworms. Generally mole tunnels disappear after the weather warms up and the moles go deeper in the ground after worms. Mole tunnels are also generally easy to push back into the ground. Voles don't make large tunnels and often prefer to use mole tunnels to move about. Unlike moles, voles are not carnivores. They are vegetarian in nature. Now, in the midwest, you could also have gophers. Gophers make very large mounds of excavated soil near their dens. There are gopher and mole traps and baits you can buy, but both can be difficult to get rid of. Voles can be controlled with standard mouse traps baited with peanut butter. There are a lot of folk tale solutions to moles, including using chewing gum in the hole, etc, but none of them work. I would go to you local garden center and look for products made by Liquid Fence. They make repellents that generally work and are not based on folklore.