The term “mole hole” often conjures an image of a small opening in the ground, but the true “hole” is a complex, subterranean network of tunnels constructed by a solitary mammal. Moles spend nearly their entire lives underground, creating extensive systems of passages. The visible sign of their activity—the molehill—is not typically the entrance to this system, but rather the byproduct of soil displacement from deeper digging. Understanding the dimensions of the mole’s habitat requires distinguishing between the excavated soil, the temporary surface runs, and the permanent, deep-level structures.
The Visible Indicator: Molehills
The most common evidence of a mole’s presence is the molehill, a cone-shaped mound of excavated soil pushed up to the surface. Mounds form when the mole clears dirt from its deeper, permanent tunnels, using a vertical shaft to deposit the material above ground. The size of these hills can vary depending on the soil type and the depth of the tunnel being dug.
A typical molehill measures between 5 and 8 inches in height, with a base diameter ranging from 12 to 24 inches across. The volume of soil displaced often reflects the mole’s digging ability. A larger molehill indicates that the animal was clearing soil from a deeper, more substantial runway beneath the surface.
The entrance to the tunnel system is usually located directly beneath the center of the mound, but the mole typically plugs this opening with loose dirt. This design ensures the tunnel system remains sealed off from the outside environment and predators. The molehill is merely a spoil pile, marking the location where a new segment of the permanent underground living space was recently excavated.
Shallow Foraging Tunnels
Separate from the molehills are the shallow foraging tunnels, which appear as raised ridges or “runs” visible just beneath the surface. These temporary, exploratory paths are created while the mole hunts for invertebrates like earthworms and grubs. These surface-level tunnels are generally only 1 to 3 inches below the grade, which is why they push up the soil to form a visible trail.
The width of the tunnel itself is narrow, measuring about 1.25 to 1.5 inches in diameter, just enough room for the mole’s cylindrical body to pass through. A mole can construct these shallow runs quickly, sometimes digging up to a foot of tunnel every minute as it searches for prey. These pathways are often used only once or a few times before the mole abandons them.
These shallow runs are characterized by their irregular, winding pattern as the mole follows the scent of food. In contrast to the deep tunnels, these surface routes are structurally weak and may collapse quickly, especially under foot traffic or heavy rain. The main function of this shallower network is to act as a pit-fall trap, where passing insects and worms fall into the passage to be collected by the patrolling mole.
Deep and Permanent Tunnel Dimensions
The deep, permanent tunnel system is the most complex and long-lasting part of the mole’s habitat, serving as the animal’s main transportation network and shelter. These main runways are located much deeper than the foraging tunnels, often ranging from 12 to 18 inches beneath the surface. This depth provides insulation against temperature fluctuations and protection from predators.
The diameter of these permanent passages is slightly larger than the shallow runs, providing a more stable pathway for the mole to traverse quickly. Within this deep system is the central nesting area, consisting of irregular chambers around the size of a quart jar, which are used for resting and raising young.
The overall territorial size of a single mole’s system can cover an area up to an acre or more, although population density dictates the boundaries. While the mole does not share its territory outside of mating season, it maintains this extensive network, which can include tunnels that reach over 70 meters in length. These deeper tunnels are the primary routes used year-round, connecting the nest to various feeding grounds and providing a secure, multi-tiered environment.