Moles disturb the ground extensively, but they typically do not leave behind the open, visible entrances associated with burrowing rodents. Evidence of their presence takes two forms: a network of subsurface tunnels and distinct conical piles of displaced soil. The damage to a lawn or garden is a consequence of these extensive subterranean excavations. These tunnels are built primarily for hunting invertebrates.
Surface Runs Versus Deep Mounds
Moles create two distinct types of structures that manifest on the surface, each serving a different purpose in their underground life. The first type is the surface run, a shallow, temporary tunnel used primarily for foraging. These runs are visible on a lawn as raised ridges or cracks in the turf, often just a few inches below the grass roots. They are formed as the mole pushes the soil upward while hunting for earthworms and grubs, and they represent the mole’s active feeding routes.
The second, more noticeable structure is the deep mound, commonly called a molehill, resulting from the excavation of the permanent, deeper tunnel system. These deeper tunnels are typically located six to twelve inches or more below the surface and serve as main travel routes, nesting areas, and resting chambers. The conical or volcano shape of the molehill is formed when the mole pushes excess dirt straight up a vertical tunnel shaft to the surface. Crucially, the entrance to the deep tunnel underneath the mound is almost always plugged with soil, meaning the mole does not leave an open hole.
The Specialized Anatomy of a Digger
The mole’s ability to create extensive underground networks is rooted in unique physical adaptations for fossorial, or digging, life. The forelimbs are its primary excavating tools, featuring massive, paddle-shaped paws that are much wider than they are long. These powerful front feet are equipped with extra-long claws and are permanently rotated outward, allowing the mole to effectively “swim” through the soil.
The mole’s shoulder girdle is significantly modified to support this powerful digging motion. Long bones like the humerus are short, robust, and possess enlarged attachment sites for powerful muscles. A specialized bone structure known as the os falciforme, or “false thumb,” extends the width of the paw, increasing the surface area for shoveling. The mole’s digging power comes from immense shoulder and chest muscles, which contribute to a unique humeral rotation that allows the animal to apply force laterally to displace the soil.
Identifying Mole Activity Versus Other Burrowers
Mole activity leaves distinctly different visual evidence compared to other common burrowing animals, such as gophers and voles. Mole mounds are characterized by their symmetrical, volcano-like shape, where the soil is pushed up from the center, and no visible open hole is present. The presence of raised surface runs, which look like veins of uplifted soil, is a sign unique to mole activity. Moles are insectivores, meaning their tunneling is driven by a search for invertebrates, not by consuming plant roots.
In contrast, pocket gophers create crescent-shaped or fan-shaped mounds. Their tunnel entrance is typically plugged with soil and offset to one side of the mound. Gophers are herbivores, and their presence suggests a threat to plant roots and bulbs. Voles rarely create large, distinct mounds; they instead leave behind small, circular entry holes and above-ground runways of clipped vegetation.