Moles can eat their weight in worms and grubs every day, so they find healthy, well-watered lawns—which are full of worms and grubs—very attractive. Tunneling as fast as a foot per minute under the sod, one mole can make an average yard look like an army invaded it.
To their credit, moles do a good job of aerating the soil and controlling Japanese beetle larvae and other harmful bugs, and they don't eat flowers or plants. If you can live with them, they generally won't cause any serious, long-term damage to your yard. However, if you can't, you'll have to trap or remove them. The population density of moles is generally no more than three per acre, so catching even one might take care of the problem.
Livetrapping by setting a deep bucket under an active tunnel is sometimes effective. To set up a live trap, dig a hole at the tunnel deep enough to set a 2- to 5-gallon bucket below the level of the tunnel. Pack the dirt around the edge of the bucket, then cover the hole with sod or plywood so you can check the hole daily. The mole will fall in, and then you can take it to a new location.
However, the most effective, time-tested method is to set up a spring-loaded prong or choker-loop trap that is activated when the mole pushes against it.
For the spring trap, flatten an area of the tunnel slightly bigger than the base of the trap and set the trap over it. Follow the manufacturer's directions to arm the trap, then cover it with a 5-gallon bucket to keep kids and pets away. Remove it and the mole after it's been triggered, or try a different tunnel if it hasn't been triggered after several days.
Whether you set up a live or a spring-loaded trap, the first step is to locate the active tunnels. Step on the tunnels you see in one or two spots to collapse them, then check those spots the next day. If the tunnel has been dug out again, it's an active one, and a good spot to set a trap.