Moles are small, subterranean mammals and a common source of frustration for property owners across North America. These insectivores belong to the family Talpidae, which includes species like the widespread Eastern Mole and the distinctive Star-nosed Mole. Moles spend nearly their entire lives underground, using specialized shovel-like forepaws to tunnel through the soil in search of food. The visible signs of their digging often lead people to wonder if they are dealing with a destructive, non-native pest.
Defining “Invasive”: Ecological Threat Versus Nuisance Pest
Confusion over whether a mole is “invasive” stems from a misunderstanding of the ecological term. An invasive species is defined as one that is non-native to an ecosystem and whose introduction causes or is likely to cause economic or environmental harm. The vast majority of moles encountered in the United States, such as the common Eastern Mole, are native species. Therefore, they do not meet the scientific criteria of being biologically invasive.
A more accurate description for moles is a nuisance species, applied to any animal that causes property damage or annoyance to humans. The damage caused by their tunneling is a byproduct of their natural behavior. While moles are not a threat to the overall ecosystem, their presence is unwelcome in a manicured lawn or garden, making them a significant property nuisance.
The Scope of Property Damage Caused by Moles
Mole activity becomes a nuisance due to the visible alterations they make to the surface landscape. One common sign is the molehill, a volcano-shaped mound of soil pushed up from deep, permanent tunnels. These mounds can range from a few inches to over a foot in diameter, disfiguring lawns and creating a safety hazard.
A second type of visible damage comes from surface feeding runs, which appear as raised, linear ridges across the turf. These shallow tunnels are located just beneath the grass roots and can collapse underfoot, making the lawn uneven and difficult to walk on. The uneven terrain created by molehills and surface runs can also damage lawnmower blades.
Although moles do not typically eat plant roots, their tunneling causes indirect damage to vegetation. As they excavate, they lift the soil, which severs or exposes plant roots to drying air. This disruption can cause patches of grass to turn brown or lead to the death of young plants and bulbs. Furthermore, the tunnels can sometimes channel surface water towards a home’s foundation, potentially exacerbating drainage and erosion issues.
Why Moles Dig: Diet and Tunnel Systems
The constant digging observed in mole activity is driven by a high metabolic rate and a demanding diet. Moles are insectivores, primarily consuming earthworms, which can account for over 90 percent of their food intake, along with grubs and other soil-dwelling invertebrates. A single mole must consume roughly 70 to 100 percent of its body weight in food every day to survive.
To satisfy this appetite, moles maintain extensive tunnel networks that function as traps for their prey. These systems consist of two main types: deep, permanent tunnels and shallow, temporary feeding runs. The permanent tunnels are used for travel, nesting, and food storage, with the excavated soil pushed to the surface to form molehills.
Shallow surface tunnels are created as the mole actively forages for food, following the movement of earthworms and grubs close to the surface. Moles prefer to dig in moist, loose soil because it is easier to excavate and supports a higher population of invertebrates. The resulting raised ridges mark these active feeding routes, which can be extended by up to 150 feet daily.
Discouraging Mole Activity Through Habitat Management
Managing mole activity focuses on making the environment less appealing to them. One primary strategy is to reduce the mole’s main food source, though the effectiveness of treating for grubs varies. While eliminating large grub populations may cause moles to leave, they will still remain if a healthy supply of earthworms is present.
Modifying irrigation practices is another simple step, as moles are strongly attracted to moist soil that is easy to tunnel through. Reducing excessive watering helps make the ground less hospitable for both the mole and its prey. Most lawns require only about an inch of water weekly, and adjusting to this level helps deter mole presence.
For high-value areas like flower beds, physical barriers can be installed to prevent entry. This involves burying a fence of hardware cloth or wire mesh at least one to two feet deep around the perimeter. The barrier should also extend a few inches above the soil line to ensure the mole cannot simply tunnel over it. Repellents containing castor oil may offer minor effectiveness when thoroughly watered into the soil, but they require full coverage to prevent moles from burrowing around the treated section.