Discovering unexplained holes in a yard is common for homeowners, often leading to concern about the health of the lawn or the integrity of subterranean utilities. These small excavations are usually the calling card of local wildlife or insects, whose activities can range from harmless to destructive. Identifying the specific creature responsible is the first step in determining whether intervention is required. The holes offer forensic clues, indicating whether the activity is temporary foraging, seasonal emergence, or the establishment of a permanent tunnel system. The size, shape, and surrounding soil conditions all contribute to solving this backyard mystery.
How to Identify Holes By Visual Clues
Accurately identifying the source of a hole begins with careful observation of several visual variables. The diameter is a primary indicator, differentiating between tiny, pencil-sized openings made by insects and wider entry points created by small mammals. The depth of the excavation is also informative, separating shallow divots caused by surface feeding from deeper shafts that lead to underground burrows.
The shape of the hole—whether round, ragged, or conical—classifies the digging tool used, such as mandibles, claws, or snouts. A major clue lies in the presence or absence of excavated dirt and its shape. Some animals leave no dirt, while others create a distinctive volcano-shaped mound, a small, crescent-shaped pile, or scattered soil around the entrance. Understanding these characteristics helps distinguish between potential culprits.
Tiny, Pencil-Sized Holes (Insects and Probing)
Holes measuring 1/4 to 1/2 inch in diameter typically signal the work of insects or the probing action of birds searching for food. This category of excavation is generally the least destructive to the lawn structure. Birds often create small, shallow, conical indentations as they peck the soil to locate earthworms or larvae, leaving no visible excavated soil mound.
Ground-nesting solitary bees (miner bees) frequently create small holes, usually 1/4 inch wide, sometimes featuring a volcano-like mound of fine soil surrounding the entrance. These solitary insects are non-aggressive, beneficial pollinators, and their nests are temporary, often disappearing after a few weeks in the spring. Another seasonal cause is the emergence of insects like cicadas or June beetles, which leave nickel-sized holes surrounded by loose soil as they exit their larval stage.
Larger solitary wasps, such as the cicada killer, dig tunnels up to one inch wide to provision their young. These holes are often found in dry, bare soil and may have a U-shaped mound of dirt at the entrance. Earthworms also leave granular pellets of soil called castings on the surface, which result from clearing their tunnels, but these rarely contain a visible open hole.
Medium Holes Associated With Mounds (Tunneling Mammals)
When holes range from one to three inches in diameter and are associated with significant soil displacement, the cause is usually a tunneling mammal establishing a permanent burrow system. Moles are insectivores that construct extensive underground networks to hunt for earthworms and grubs. They are identified not by an open hole, but by the distinctive, cone-shaped or volcano-like mounds of dirt pushed up to the surface. These mounds, which can be 1 to 2 feet wide, do not have a visible entry point in the center because the mole plugs the hole from below.
Moles also create surface tunnels, which appear as raised ridges in the lawn, typically three inches wide, that flatten easily when stepped on. In contrast, voles, which are small, plant-eating rodents, create clean, open entry holes about 1 to 1.5 inches wide. Vole holes typically lack the large, conical dirt mound of a mole, often having only a small dirt pile next to the entry point, or none.
Voles do not create the raised ridges seen with moles, but instead make shallow, two-inch-wide surface runways through the grass, which look like well-worn paths connecting multiple burrow openings. Chipmunks are another common tunneling mammal; their holes are often described as silver dollar-sized and clean, lacking significant dirt piles. Chipmunk burrows are frequently located near structures, trees, or brush piles and are used for shelter and food storage.
Irregular and Shallow Digging (Nocturnal Foragers)
A distinct type of lawn damage involves irregular, shallow excavations that result in torn or disturbed turf rather than a clean, deep entry hole. This activity is characteristic of nocturnal foragers searching for insects and larvae near the surface, particularly white grubs. Skunks, using their acute sense of smell, are common culprits, creating numerous small, conical or scoop-shaped holes.
These holes, which may be two to three inches across and look like small divots scooped out with a spoon, result from the animal pushing its nose into the soil and using its front paws to dig out a targeted grub. The damage is generally spread across the lawn, often concentrating in areas with the highest grub population. Raccoons, which possess more dexterous front paws, cause more aggressive damage.
Raccoon foraging typically involves lifting and flipping larger sections of sod, creating aggressive patches of torn turf. The damage can look like the grass has been neatly rolled back or scattered in mats, as the raccoon uses its strength to peel back the turf to access the food source. The overall pattern for both skunks and raccoons is characterized by surface-level rooting and tearing, providing a clear distinction from the deep tunneling of moles and voles.