Finding a hole in the ground prompts immediate curiosity about the unseen animal responsible. These openings are distinct markers left by a wide variety of animals, which use them for shelter, hunting, or breeding. Identifying the creature requires careful observation of the hole’s dimensions, the surrounding soil structure, and its location within the landscape. Focusing on the visual evidence left on the surface helps determine which animal is using the subterranean space.
Large Burrows and Permanent Dens
Holes four inches or greater in diameter usually signify a primary, long-term residence used by medium-to-large mammals. Groundhogs, also known as woodchucks, create substantial burrows with entrances up to 12 inches across. These entrances often feature a large, crescent-shaped fan of excavated soil extending outward. Their extensive tunnel systems frequently include multiple secondary entrances for escape and are often strategically dug under structures like sheds or decks for protection.
Carnivore dens, such as those belonging to foxes and coyotes, are generally larger and more complex, sometimes involving multiple entrances. Fox dens have openings between 6 and 12 inches in diameter, distinguished by a trampled “throw mound” of dirt from the activity of the parents and pups. Coyote dens are larger, often exceeding one foot in width, and may appear triangular or elliptical; they frequently repurpose and enlarge existing burrows. Skunk entrances are smaller, typically a round hole about four to six inches in diameter, and they prefer digging these under porches or low-lying foundations.
Distinctive Mounds and Surface Tunnels
Many subterranean dwellers are identified by the distinctive mounds of dirt they push up to the surface, rather than an open hole. Moles are insectivores that create two primary signs of activity: volcano-shaped mounds and raised surface ridges. A molehill is a symmetrical, conical pile of finely sifted soil, often with a soil plug visible in the center, pushed up from a deep, vertical tunnel.
The raised ridges, sometimes called surface runways, are shallow tunnels just beneath the grass that moles create while actively hunting for earthworms and grubs. Gophers, in contrast, are herbivores that produce crescent- or horseshoe-shaped mounds of dirt that are flatter on top. The hole that the gopher used to push the dirt out is typically plugged with soil and located off to one side of the mound, a characteristic that differentiates it from the central plug of a molehill.
Pinholes, Exit Holes, and Temporary Dwellings
Smaller holes, generally less than two inches in diameter, belong to small rodents or insect species and often serve a temporary purpose. Voles create dime-sized holes, usually one to one-and-a-half inches across, that are neat and lack a dirt mound around the opening. These tiny burrows are frequently concealed under dense vegetation and are connected by narrow, visible runways of clipped grass on the surface.
Insects account for many small holes, particularly the periodical cicada, which leaves behind perfectly round exit holes about a half-inch in diameter when emerging for its final molt. In wet soil, cicada nymphs sometimes construct miniature mud “turrets” or “chimneys” around the exit hole. Solitary bees create some of the smallest entrances, from one-sixteenth to five-eighths of an inch, by excavating into bare, well-drained soil or nesting in existing tubular cavities. The female bee seals the entrance with mud or leaf pieces after provisioning the individual egg cells.