I have voles in my backyard. How...

You have to make your yard inhospitable to them. Voles like dense, heavy vegetative cover, mulch, and weeds because it provides them with food and protects them from predators. If you remove these things, you’ll discourage voles. Next, locate the areas where they feed by setting out food. Once you’ve pinpointed these spots, decide whether you want to try to trap them or bait them with a registered rodenticide. Another great control method might be an outdoor cat.