Moles are insectivores whose constant tunneling creates the familiar upheaval in lawns and gardens often called a “mole hole.” This term oversimplifies an intricate, three-dimensional system designed for hunting and shelter. Understanding the size and function of these structures—the raised ridges, conical dirt piles, and deep, permanent runways—is essential for managing their presence. The visible evidence is only the tip of a complex underground network.
Distinguishing Mole Structures: Mounds Versus Tunnels
Mole activity is visible through two distinct structures. The first is the molehill, a volcano-shaped pile of soil resulting from deep tunnel excavation. The mole pushes excess dirt vertically to the surface through a central, plugged opening.
The second structure is the tunnel itself, which includes surface runs and deep main runways. Surface runs are shallow, temporary pathways appearing as raised, spongy ridges across a lawn. These feeding runs are used primarily for foraging earthworms and grubs just beneath the grass roots.
Deep tunnels are the permanent infrastructure of the mole’s home range. These stable, frequently used highways connect foraging areas with the central living quarters, providing a secure route for travel. The soil excavated from these deep tunnels forms the conspicuous molehills on the surface.
The True Dimensions of Tunnels and Mounds
The actual size of a mole’s tunnel system is extensive, with dimensions that vary based on the tunnel’s function and the specific species. Permanent, deep main runways are typically constructed to be between 1.5 and 2 inches in diameter, a comfortable fit for the animal’s body. These travel routes are usually found at depths ranging from 10 to 18 inches below the surface, though their depth can extend further depending on soil conditions.
Surface feeding runs are much shallower, often lying just 2 to 3 centimeters beneath the soil. This shallow depth is why they create easily visible ridges across the ground. A single mole’s territory is extensive, with the entire tunnel network sometimes exceeding 1,000 meters in total length.
Mole hills indicate deep excavation work. A typical molehill is a cone-shaped pile measuring 4 to 6 inches high and up to a foot in diameter at the base. The mound size is proportional to the difficulty of the soil, with harder digging resulting in larger, less frequent piles of displaced soil.
Anatomy of the Central Nesting Chamber
The central nesting chamber is a specialized, larger structure distinct from the general runways. It is typically situated deep underground, often 1 to 3 feet below the surface, where temperatures are stable and the structure is protected.
The chamber is a spherical space, about the size of a quart jar, and is lined with soft, dry plant material like grass, leaves, and roots to create a nest. This space serves as the primary den for resting and where the female mole raises her annual litter of pups.
In areas with shallow soil or a high risk of flooding, a mole may construct a “fortress.” This involves building a much larger, prominent mound above the nesting chamber. The fortress contains a significant volume of soil and helps insulate the nest, providing refuge.
Identifying Mole Activity Versus Other Pests
Distinguishing mole activity from other burrowing animals like gophers or voles requires observing the distinct architectural signatures each creature leaves behind. The mole’s calling card is the volcano-shaped molehill, formed by pushing soil straight up through a central, plugged opening. The visible, raised ridges traversing the lawn are definitive signs of a mole’s shallow feeding tunnels.
Gophers, which are rodents, create a noticeably different mound structure. Gopher mounds are typically crescent-shaped or fan-shaped, and the excavated soil plug is located off to one side of the mound, not centered. Their tunnels are often deeper, and they do not create the raised surface ridges characteristic of mole activity.
Voles are small rodents that primarily feed on plants and roots. They create tiny, circular burrow entrances, usually 1 to 1.5 inches in diameter. Their activity includes visible, narrow runways or trenches worn into the grass at the surface. Voles do not create the large, conical dirt mounds that moles or gophers do.