There are six species of moles in North America, and three of these may occur in your yard (Eastern Mole, Hairy-tailed Mole, and Star-nosed Mole). Moles are about the size of chipmunks (6-8 inches in length) and can weigh three to six ounces. Each year a mole can have one litter of two to six young, depending on the health of the female. Gestation lasts about five to six weeks, which means that you can expect litters anywhere from mid-April through May.
Moles are insectivores (they eat insects), and they may control some insect outbreaks. However, mole activity can also cause considerable damage to lawns. This damage is usually in the form of tunnels and/or mounds in lawn that can be unsightly, disturb root systems, and provide cover or travel lanes for other small mammals.
Moles can quickly colonize and spread through adjacent residential properties if not handled properly. Because they need a well-established tunnel network to survive, control will be more difficult the longer they are allowed to tunnel and become habituated.
On large properties mole activity may move from one part of the lawn to another. This movement is affected by climate and ground moisture. Moles will respond to changes in food supply as different insects become available in different places and at different times throughout the year. If disturbed, moles may temporarily leave an area but will usually return when you least expect it. Even without disturbance mole activity may last only a week or two in a particular area.