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Gardening: Moles, voles, tunnels and holes

“Honey, there’s a hole in the garden!” are not words any gardener wants to hear, especially when the hole happens to be very close to a prized plant. It can be tricky to identify the critter by the hole, but two of the most common tunneling pests in our area are moles and voles. Although their rhyming names can cause confusion, only one of these makes a meal of your plants.

Moles: If you have raised tunnels in your yard, moles are probably to blame. Moles are 4 to 6 inches in length, have small eyes and concealed ears, and paddle-like front feet designed for digging. They tend to be solitary creatures, and 3-5 moles per acre is considered to be a high population. Moles dig deep tunnels where they bear their young and retreat during very dry or cold weather. Conical piles of excavated soil often cap these deep tunnels. The deep tunnels connect to a constantly expanding and changing network of feeding tunnels located just below the surface of the soil or turf. Entrances to dens may have mounds of soil – molehills – around them. Moles don’t eat plants, but their tunnels can cause damage by disturbing the root systems of plants growing above them. These tunnels are where moles hunt for grubs, earthworms, and other invertebrates that make up their diet. Some of the grubs and insects in moles’ diets are lawn and garden pests. Mole tunneling also helps to aerate the soil, which can improve drainage and move mineral nutrients and organic matter around. Still, the tunnels’ damage to the landscape causes many homeowners frustration. Moles use and renew some of the surface tunnels repeatedly. Others may be used only once. Traps must be set in active tunnels. You can determine whether a tunnel is active by stepping on it to compress the soil. If it is active, and a good trapping site, the mole will raise the soil or turf again within 24 hours.

Note: “Home remedies” such as gum or glass shards have not been shown to be effective.

Voles: Voles, also known as field mice, are small brown rodents very common in yards and fields. They have small ears and a short tail, which give them a “stocky” appearance. They spend a great deal of time eating grasses and roots and making trails. These surface runways are one of the easiest ways to identify voles. Usually seen in early spring just after snowmelt, a series of criss-crossing trails can be viewed on the surface. There may be larger patches of dried grass that function as storage areas for extra food and nesting materials.

Voles will also make small holes about 1to 2 inches across and underground tunnels to get to tubers and bulbs. They will even use mole tunnels. This is the reason moles are blamed for eating roots, instead of the white-grubs they actually eat. Voles do the most harm to small trees and shrubs when they chew on the bark, often hidden below winter snows. Valued plants can be protected by using a barrier (such as hardware cloth) or planting in pots, but this may not be feasible for large shrubs and trees.

Minnesota has several species of vole, the most common being the meadow vole (Microtus pennsylvanicus) and the prairie vole (Microtus ochrogastor). Like most rodents voles have a short life expectancy but are very prolific breeders. One female vole can have 5-10 litters in a year averaging 3 to 5 young. Voles prefer to have some protection from predators. To make your yard less attractive to voles, keep grassy and weedy areas mowed, and do not mulch deeply.

Chipmunks: Chipmunks (Tamias striatus) are a type of ground squirrel that live in wooded areas and around homes where food is plentiful. The chipmunk has five dark brown stripes, which run from its head to its rump. It scurries about with its tail straight up (looking like a zooming remote-control car). Like moles and voles, chipmunks live in underground tunnels. Chipmunks are omnivores, eating a variety of foods including seeds, nuts, berries, and insects. Some food is stored for winter in their burrows. Although they are not usually a major nuisance in the landscape, chipmunks can feed on flower bulbs and seeds for vegetable gardens. They also can burrow under foundations, patios and sidewalks, which may cause structural damage. Hardware cloth or other barriers can be used to keep chipmunks from tunneling under sidewalks or entering buildings. Reducing cover for chipmunks and keeping bird feeders away from structures will make your house less attractive to them. Repellents can be used but must be reapplied frequently.

Ground Squirrel: The 13-lined ground squirrel has 13 lines on its back, some spotted, which run from its head to its rump. Also known as the striped gopher (Spermophilus tridecemilineatus) or 13-liner can reach 11 inches in length including a 4 inch black lined tail. The holes to the tunnels are about 2 inches wide. The 13-lined ground squirrel is a common pest in and around building foundations, golf courses, gardens and lawns, but it prefers open grasslands where it feeds on equal amounts of plants and animals. Its diet includes insects, grasshoppers, moths and butterflies, earthworms, young birds and mice, seeds, fruits, nuts, roots, and foliage. At the end of summer, the 13-lined ground squirrel will fatten up for hibernation.

Note: These animals really do have 13 stripes — seven dark stripes separated by six lighter ones. The 13-liner is very familiar to Minnesotans because this little animal is the mascot for the University of Minnesota’s “Golden Gophers!”

These are not the only animals that could be digging in your yard. An environmentally friendly approach to a “mystery hole” would be to observe the area to find the hole’s owner, then assess whether the animal is likely to cause enough damage to require treatment. You can go to the University of Minnesota website: http://www.extension.umn.edu/garden. Type the animal you suspect in the search box.

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