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Moles: Damage Management

With a habit of burrowing and creating unsightly tunnels that damage roots and weaken the surface of lawns, the eastern mole (Scalopus townsendii) has established itself as an annoyance in yards across Iowa. Fortunately, tried and true methods are available to help keep this invader at bay.

Habitat: The eastern mole is a common inhabitant of meadows, pastures, lawns, cemeteries, playgrounds, golf courses, sports fields, parks, open woods, and stream banks. Moles are especially attracted to areas with a steady supply of soft-bodied invertebrates (earthworms and grubs) to eat and soil that is moist but well-drained for ease of burrowing. Sandy or loamy soils provide ideal habitat, while heavy clay soils and excessively rocky or compacted soils are less appealing for burrowing. However, moles sometimes manage to tunnel through seemingly unsuitable soils to reach preferred areas, causing characteristic damage along the way.

Diet: The eastern mole’s habit of actively pushing or “swimming” through soil requires considerable energy. As such, a mole must consume nearly 100% of its body weight each day. Although they are often mistakenly thought of as plant eaters, moles are predators that use their exceptional sense of touch to capture invertebrates, such as centipedes, earthworms, grubs and other insects. Seed pods and other vegetable matter make up a much smaller proportion of a mole’s diet. Therefore, the damage caused by moles is primarily the result of tunneling, not the direct consumption of plants.

General biology: The eastern mole is a solitary animal except when mating, which occurs in late winter or early spring. Three to five young are born after a gestation period of six weeks. The young grow quickly and leave the underground nest chamber at about one month in age. Rainy days during late spring and summer usually trigger the greatest level of activity in moles, as they frantically gather food during this time. Prolonged periods of rain are an annual source of mole mortality. Drier conditions cause moles to burrow more deeply into the soil. Because moles do not hibernate, these deeper tunnels serve as year-round food resources, which are especially important during harsh winters. Their underground lifestyle also keeps them safer than most small animals, although raccoons, badgers, skunks, foxes, coyotes, and dogs sometimes dig moles out of their burrows and hawks and owls occasionally snatch moles from the surface.

graphic depicting underground mole activity, feeding tunnels, mounds, runways, and trap placement
Mole burrow system showing appropriate trap placement on a long, straight stretch of tunnel.

Damage identification

Once a mole invades a yard, it can cause considerable damage almost immediately, especially when in pursuit of prey. In fact, a single mole can tunnel up to 18 feet per hour in suitable soil. A key to managing moles and curtailing their conspicuous damage is first correctly identifying their sign:

  • Volcano-shaped mounds of soil with no entrance or exit holes are pushed up from deep below the soil surface.
  • Raised linear ridge(s) of soil running through grass of lawns that ultimately become a complex network of multiple lines entering and exiting yard 
  • Mounds and ridges are most common in the shaded portions of lawns and similar sites
  • Soil around ridges and mounds feels soft and spongy.

Pocket gophers can invade some of the same areas as moles. However, pocket gophers build large, crescent-shaped dirt mounds, which often have a 1-3 inch wide plug in the middle where the gophers exit the ground to feed on the surface (which moles never do). These structures are distinct from the conical or volcano-shaped mounds and raised ridges made by moles. Meadow voles make narrow runways along the surface of grassed sites, which differ from mole runways beneath the soil surface.

 

side by side comparison of volcano shaped mole mound and crescent shaped gopher mound
Mole mounds (left) are volcano shaped whereas pocket gopher mounds (right) are crescent-shaped and have a plug of dirt at the top of the tunnel.

Removal of Nuisance Moles

Trapping is the most effective and safe method of removing moles. Two commonly available trap types are sold at hardware and farm stores and can be targeted to capture moles in the same way. The key to successfully capturing problem moles is setting traps in the right places. Follow these suggestions for finding the right places for traps

  • Place traps along long stretches of tunnels that moles most frequently use. Traps are not effective on mounds.
  • Target long, straight stretches of tunnels or places where tunnels enter or exit the yard.
  • Avoid tunnel sections with lots of bends ot twists.
  • Stamp down the top of all the tunnels in your yard on one day and return the next to find which tunnels are frequently used. Some tunnels are runways while others are used only occasionally for feeding. You want to target traps on runways used regularly.

scissor-jaw trap and harpoon trap
Scissor-jaw trap (left) and harpoon trap (right).

Setting a scissor-jaw trap

  • Excavate soil at the targeted section to expose the underground tunnel.
  • Replace excavated portion with loosely packed fine soil.
  • Force the jaws of the trap directly into the soil until the trigger pan rests on the repacked soil surface.
  • Make sure the jaws are aligned as evenly as possible on either side of tunnel, with the points of the jaws about 1 inch below the bottom of the tunnel.
  • Push the jaw levers apart to lock them into place; many scissor-jaw traps have a hair-trigger mechanism to make them spring more easily.
  • Fill the hole on top of the trap with loose soil and ensure that no obstructions will interfere with the closing jaws.

Setting a harpoon trap

  • Press down on the ridge of tunnel to allow space for the trapping mechanism.
  • Raise the spring and set the safety catch.
  • Push the spikes into the ground so that the tunnel runs between them; make sure the “trigger pan” rests right on the ground above the tunnel
  • Release the safety catch (this enables the impaling spike to be forced down into the ground by the spring)
  • Set the trap and leave it; avoid walking on any portion of the tunnel system
  • If the trap is set properly, the impaling spike will shoot down through the burrow when triggered by the mole.

Weighing costs versus benefits: Before you set out to eliminate moles from your property, consider the following: moles play an important role in soil aeration and fertilization, along with consuming harmful insects and grubs. For instance, moles prey heavily on the “white grubs” that ruin vast sections of lawns and golf courses. As such, determine whether removing a mole and its associated damage is worth the resulting increase in lawn pests. Furthermore, when you remove a mole, another one may quickly move in, leading to an ongoing removal process.

This article is an update of "Managing Iowa Wildlife: Moles" (PM-1302b) originally authored by Kurt Johnson and James Pease.

Burrowing Mammals

Biologists call them fossorial -- animals that live or spend a considerable amount of their time under the ground. Most homeowners simply call them annoying.  What’s going on with those wildlife as they dig holes, often most conspicuously late in the summer and fall? 

Woodchuck DamageMost of these wildlife are in search of places of shelter, where they will spend the majority of the winter out of the elements. Chipmunks are in search of seeds, berries and other fruits, which they are eating for extra calories or stashing away in so-called middens, basically underground pantries, for use throughout the winter. Raccoons and skunks are munching on various fruits and rummaging through the sod in search of juicy grubs to fatten up for their less active winter wanderings. Similarly, woodchucks, or groundhogs, are fattening up on various fruits, seeds and greens, including those in your vegetable gardens, before they settle into their dens to hibernate.

Between meals, these mammals will either burrow into the soil to create a den or find shelter within or underneath anything that offers cover. This can occur behind retaining walls, along foundations, and underneath walkways, storage sheds, crawl-spaces and decks, to name a few. Most problems occur around decks, storage sheds, and houses with crawl-spaces. Such areas are perfect shelter for a variety of wildlife. Fortunately, with a little extra planning and effort, you can easily design or retrofit these places to prevent most damage caused by burrowing wildlife.

Trapping

Trapping, or hunting, is often the last resort in cases of nuisance wildlife. In some cases, trapping may not be necessary if physical alterations around the yard and changes in our behavior are done first. Exclude access, described in the next section, to spaces with overhead cover. Feed pets indoors and store pet food in sealed containers, preferably indoors. Set garbage out in the morning before pick-up. And while some of these offer cover for desirable wildlife, remove loose piles of debris, such as scrap lumber, boards, metal sheeting, tires, rocks, and brush around your house in areas wildlife aren’t welcome.

If the critter is already causing damage, as in the case of a woodchuck digging its winter burrow, trapping or shooting may be your first order of business. Follow appropriate trapping and hunting techniques and regulations for nuisance wildlife, and remember, shooting is not a suitable option if you live in town. Also recall that many wildlife are protected either as game species (like stripped skunks, badgers, and foxes) or because of another legal status like being threatened of extinction and thus are protected. Check with your local Conservation Officer before using lethal control. 

Live-trapping the offending critter(s) is often the most prudent course of action. Wire drop-door traps, or live traps, are effective at trapping any of these species and are readily available for purchase at local hardware or farm stores. Some traps may also be available to borrow from animal control departments or possibly a county conservation board.

Trap placement is important. Most wildlife species are creatures of habit, and usually have a designated route (lane) that may be visible as a worn path in the yard. Place the trap in the direction of travel in the lane nearby burrows or where you see evidence of their activity. To encourage the animal to enter the trap, create a “funnel” into the opening using logs as barriers on either side of the entrance. In the case of woodchucks, they usually have two or more burrow entrances, and secondary entrances are often well hidden and difficult to find. More than one trap may improve trapping success.

Traps should be baited with the preferred food. For woodchucks, fresh-cut apples tend to work best, but you can also try other fruits such as strawberries, cantaloupe, and grapes. For striped skunks and raccoons, an open can of oily sardines or canned dog or cat food will work just fine. The trap may be baited 2-3 days with the trap door wired open so that the animal gets accustomed to available food. This is known as "pre-baiting" and may improve your trapping success. Check a trap twice daily, both morning and evening. Once the animal is trapped, it can be moved, but must be released at least 5 miles away in suitable habitat to prevent its return to your yard. When releasing, respect private property and avoid releasing the animal in a location where it may cause further damage.

Exclusion

Deck Fencing Example Once the offending animal is removed, repair any damage caused by digging. Then exclusion can begin. Burrowing and access can be prevented up front by creating a barrier in front of potential places of shelter. Because most people have problems with decks, storage sheds, and homes with crawl spaces, the following describes how best to exclude underneath these, although similar techniques can be used in other places where digging occurs, such as along cement slabs and walkways and along foundations.

Fencing can be placed below any exposed space. This is done using 1/2 inch mesh hardware cloth, which usually comes in 2 or 3 foot wide rolls and can be purchased at your local hardware store. First, dig a narrow trench along the entire perimeter of the structure and bury the mesh 10-12 inches below ground. Bring the exposed mesh up to the bottom of the structure and attach it firmly to the deck frame or bottom of the home or shed, making sure there are not loose sections. A picture is included showing this technique on a deck. This should exclude shelter seeking critters for years to come. 

Photo Credits: Woodchuck damage, http://icwdm.org; Deck fencing exclusion, Jim Pease Iowa State University