Yard tunneling is a common homeowner issue that results from the subsurface activity of small mammals moving and foraging underground. While the visible damage is often similar, identifying the specific animal responsible is the necessary step toward resolving the problem effectively. The tunnels, mounds, and surface trails each animal creates serve as distinct clues that point to the culprit.
Distinguishing Between Tunneling Animals
The most common tunneling mammals are moles, gophers, and voles, differentiated by the structure of their mounds and tunnels. Moles create two structures: volcano-shaped mounds and raised ridges. Molehills are symmetrical, circular piles of fine, sifted soil pushed up through a vertical shaft, rarely having a visible entry hole at the center.
Moles are insectivores, feeding on earthworms, insect larvae, and grubs, and they do not eat plant roots. Tunneling is a byproduct of constant foraging; they must consume nearly their body weight in food daily to maintain their high metabolism. Some species can dig up to one foot per minute in loose soil.
Gophers (pocket gophers) create crescent or fan-shaped mounds. These mounds form when the gopher pushes soil out of its main tunnel, leaving a distinct, plugged-off entrance visible on one side of the pile. Gophers tunnel deeper than moles, with feeding tunnels typically 6 to 12 inches below the surface and nesting chambers sometimes six feet deep. They are herbivores that feed on roots, tubers, bulbs, and vegetation, often pulling entire plants down into their tunnels.
Voles leave behind small, open entry holes and visible surface runways in the grass. The entry holes are clean, round openings about 1.5 inches in diameter. Runways are narrow, clipped trails in the turf where voles have eaten the grass and traveled repeatedly. Voles are herbivores and will gnaw on the bark of young trees and shrubs, or consume plant roots. Unlike moles and gophers, voles may use existing tunnels to access plant roots, which can sometimes lead to misidentification.
The Impact of Subsurface Activity on Yards
Subsurface activity affects plants, turf, and underground infrastructure beyond cosmetic damage. Herbivorous animals like gophers and voles inflict direct damage by consuming roots, bulbs, and the bark of woody plants. Girdling, where voles chew the bark around the base of a tree, cuts off the flow of nutrients and water, potentially killing the plant. Gopher tunneling can cause the sudden wilting or disappearance of garden plants as root systems are severed or consumed.
Mole activity, while not directly plant-consuming, damages lawns through the creation of raised surface ridges and mounds. These runways lift the turf away from its roots, causing the grass to dry out and turn brown. The soft, spongy soil over their tunnel systems can create tripping hazards. Furthermore, the constant digging by all three animals can compromise underground systems, causing damage to irrigation lines, sprinkler heads, and buried utility lines.
The tunneling process does have a positive effect on the soil. The movement of soil helps aerate the earth and mixes organic material throughout the layers. For most homeowners, however, this benefit is outweighed by the destruction of maintained lawns and gardens.
Practical Strategies for Tunnel Management
Management begins with habitat modification, focusing on making the yard less appealing to the pests. Since moles are driven by their insectivore diet, reducing their primary food source through professional grub control makes the area unappealing for foraging. For voles, which seek cover and food, removing dense vegetation, keeping the lawn closely mowed, and clearing away heavy mulch or fallen birdseed reduces their protective habitat and food supply.
Physical barriers offer an effective exclusion method, particularly against gophers and voles. Lining the bottom and sides of raised garden beds with galvanized hardware cloth (1/4 inch mesh or smaller) prevents access from below. For new plantings, individual wire baskets can be placed around the roots of trees and shrubs to protect them from consumption. For a comprehensive barrier, an underground fence of hardware cloth buried 24 to 30 inches deep and angled outward can deter burrowers.
For established infestations, lethal control through trapping is effective, especially for moles and gophers. Various trap types, such as scissor, choke, or snap traps, are designed to be placed directly into active tunnels or runways. Success relies on accurate identification of the active tunnel and correct trap placement to intercept the animal’s movements.
Chemical and sonic repellents are used, but their effectiveness is temporary or localized. Repellents based on castor oil create an unpleasant odor and taste in the soil that deters moles and voles, but they must be reapplied frequently. Sonic or vibration-producing devices are not recommended as a standalone solution because animals become accustomed to the noise or tunnel around the disturbance. If the infestation is large, recurring, or threatens infrastructure, consulting a professional pest control service is the most reliable course of action.