Moles are subterranean insectivores whose presence is often first revealed by signs of their extensive digging activity on the surface. These mammals spend nearly their entire lives underground, creating complex tunnel networks as they search for food. The most visible evidence of this activity is the molehill, a distinct pile of soil that signals a disturbance to the lawn or garden. Identifying this feature is the first step in understanding the extent and nature of the activity in the soil.
The Defining Features of a Molehill
A molehill is instantly recognizable by its distinct, symmetrical shape, often described as a miniature volcano or a perfect cone. This structure forms when the mole excavates deeper tunnels and pushes the excess soil vertically up to the surface through a central shaft. The resulting mound typically presents as a circular pile of soil, usually spanning only a few inches in diameter.
The soil texture in a molehill is a defining characteristic, consisting of finely sifted, loose earth. Moles push the soil from below, meaning the material is often uniform and crumbly, lacking large clumps, rocks, or pieces of turf. At the center of the conical mound, one can find a small, concealed plug of dirt that covers the exit hole. This central plug confirms the vertical nature of the tunnel below, as it is the spot through which the mole ejected the excavated soil.
Distinguishing Molehills from Other Soil Mounds
While a molehill is conical with a central soil plug, the most common look-alike, the gopher mound, exhibits a different structure. Gophers create mounds that are characteristically crescent or fan-shaped, signifying that the animal pushed the dirt out of a lateral tunnel opening. The entrance to a gopher burrow is typically found off to one side of the mound and is usually sealed with a visible plug of soil.
Gopher mounds are substantially larger than molehills, often reaching diameters of 10 to 20 inches. The soil used to construct a gopher mound is frequently clumpy and less uniform than the finely textured earth found in a molehill. This difference reflects the distinct digging styles and tunnel purposes of the two animals.
Other surface disturbances are less likely to be mistaken for a molehill. Voles, which are small rodents, rarely create large soil mounds; instead, they leave behind small, open holes, often only an inch or two across, near plant roots. Ant hills and worm castings also create small piles of soil, but these are significantly smaller and less disruptive than the excavation mounds created by moles. Understanding the shape, size, and location of the soil pile confirms the source of the digging.
Understanding the Associated Tunnel Systems
The presence of a molehill signals the excavation of a deep, permanent tunnel. Moles dig these main tunnels to establish nesting chambers and primary travel routes, which typically lie between 6 and 12 inches below the surface. The excavated soil from these deep systems must be expelled, and this disposal results in the formation of the surface molehill.
This activity is distinct from the other primary sign of a mole’s presence: the raised ridge or surface runway seen tracing an uneven line across a lawn. These raised ridges are temporary, shallow foraging tunnels created just beneath the turf as the mole searches for earthworms and grubs. The mole pushes the soil up to create the tunnel ceiling but does not dispose of the earth on the surface, which is why these runways feel soft or spongy when stepped on.
A single mole may establish an extensive network of both deep tunnels and shallow surface runways across its territory. The surface runways are used for hunting and are often abandoned. Molehills mark the access points for the more established, deeper sections of the tunnel system, representing the most significant, long-term structural digging activity of the animal.