A yard full of unexpected holes is often caused by a variety of wildlife, insects, and non-living factors, ranging from harmless foraging to structural tunneling. Identifying the source requires careful observation, as the size, shape, and surrounding debris of the hole offer precise clues about the culprit. Moving from general observation to specific identification is the most effective way to determine the cause and decide on the appropriate course of action.
First Steps in Hole Identification
Before attributing a hole to any specific animal, systematically examine the damage. The most critical piece of information is the hole’s diameter, which immediately narrows the list of potential culprits. Holes smaller than one inch point toward insects or very small rodents, while openings three inches or wider suggest a larger surface-dwelling animal.
The shape of the excavation also offers a significant clue to the animal’s behavior. A perfectly circular, clean-cut opening suggests a deliberate den entrance, while a shallow, conical, or ragged hole often indicates foraging for food. The location of the hole—whether in the open lawn, near a foundation, or under dense shrubbery—can also indicate the creature’s preference for cover or structural stability.
The presence and nature of the displaced soil is the most telling characteristic for burrowing animals. Observe if the dirt is scattered over a wide area, pushed into a distinct, symmetrical mound, or piled into an asymmetrical, plugged heap. Scattered soil is common when an animal is hunting for grubs, while a defined mound indicates a significant subsurface tunneling operation. These four factors—size, shape, location, and debris pattern—allow for an accurate diagnosis.
Small, Clean Holes: Insect and Burrowing Rodent Activity
Holes one inch or less in diameter that lack significant dirt mounds are typically the work of insects or smaller burrowing rodents. Ground-nesting bees and wasps create some of the most common small holes, often appearing in areas of thin or bare turf. Solitary ground-nesting bees, which are non-aggressive pollinators, leave openings approximately one-quarter inch wide with very little soil piled around the entrance.
Cicada killer wasps are larger and create a more noticeable opening, usually around one-half inch in diameter, often featuring a smooth, vertical shaft. These burrows may have a small, fresh pile of dirt piled at the entrance, unlike the nearly invisible entrances of the smaller ground bees. Other small, neat holes can result from the mass emergence of insects like cicadas or June beetles, which leave behind small, nickel-sized holes as they exit the soil.
Small rodents, particularly voles, also create holes in this size category, typically between one and two inches wide, rarely surrounded by a dirt mound. Vole activity is best identified by the presence of surface runways—narrow, above-ground paths created by the rodent pushing down the grass. These herbivores feed on roots and plants, and their holes are often hidden under thick mulch or dense vegetation.
Mounds and Tunnels: Identifying Subsurface Excavators
When a hole is accompanied by a substantial mound of soil, the cause is almost certainly a dedicated subsurface excavator, most commonly a mole or a gopher. Distinguishing between them requires a careful look at the shape of the dirt mound, as their tunneling methods are distinctly different. Moles create characteristic volcano-shaped or cone-shaped mounds that are symmetrical, with the actual entrance hole often centered and plugged with dirt.
Mole tunnels appear as raised, linear ridges that wind across the lawn surface, indicating the shallow depth at which the animal is searching for food. These insectivores primarily feed on earthworms and grubs, and the ridges feel soft or spongy when stepped on. The mole pushes excess soil straight up to the surface from a deep tunnel, forming the symmetrical molehill.
Gophers, conversely, create asymmetrical mounds, often described as horseshoe-shaped or fan-shaped piles of dirt. The entrance to a gopher burrow is off to one side and is typically plugged with soil. These rodents are herbivores that feed on roots and plants. Their tunnel systems are deeper, usually four to eighteen inches below the surface, meaning they do not leave the raised surface ridges associated with mole activity.
Larger Surface Excavations and Non-Animal Causes
Larger holes, generally three inches or more in diameter, are caused by animals digging for food or shelter, or by non-biological factors. Skunks are a frequent cause of lawn damage, creating numerous, shallow, conical holes as they systematically dig for subsurface grubs and insects. These foraging holes are usually only a few inches wide and deep, appearing as small, upturned patches of turf.
For shelter, larger mammals like woodchucks (groundhogs) create massive burrows with entrances that can be eight inches or more across. These structural entrances are often located near foundations, under decks, or in dense brush, and are typically marked by a large mound of displaced dirt. The hole itself is usually round.
Beyond wildlife, a hole may indicate a non-animal cause related to soil instability or infrastructure. Settling soil can occur when buried organic material, such as old tree roots or construction debris, decomposes and collapses, creating a sinkhole-like depression. These holes often appear suddenly and may be much larger than any animal burrow.
Infrastructure and Utility Issues
Other causes include utility access points, such as septic system inspection caps covered by grass, or erosion from a leaking underground irrigation pipe that washes away the soil.