Vole and Mole Damage in Northern Colorado: How to Tell Them Apart (Johnstown, Loveland)

1) First: it is probably not a mole

A mole is a specialized underground insectivore with a slender hairless pointed snout and short sparsely haired tails. It pushes shallow tunnels up into raised ridges, does not eat plants, and does not leave mounds of soil.

CSU Extension's "Burrowing animals: determining species by burrows & damage" fact sheet states that moles are rarely found in Colorado and only on the eastern plains, along the Lower South Platte and in the Cimarron watershed. The Front Range is not mole country, and the fact sheet is blunt: damage blamed on moles is most likely done by another species. The realistic suspects are voles, pocket gophers, prairie dogs, and Wyoming ground squirrels. On irrigated Front Range ground — the South Platte corridor, the open spaces north of Johnstown, the ditch water along eastern Weld County — meadow and prairie voles are most likely in your turf.

2) How to tell voles, gophers and moles apart

• Voles (4 to 8.5 inches long). Brown to gray, pudgy, blunt faces, small eyes and ears. You will see surface runways 1 to 2 inches wide through matted grass, open holes 1 to 2 inches across, and spongy soil from burrowing. On trees and shrubs, gnaw marks about 1/16 to 1/8 inch wide in irregular patches, with pointed tips on the stems.
• Pocket gophers. Almost never seen above ground. They leave fan-shaped mounds with closed entrances, eskers — solid tubes of soil where snow melts in spring — and plants that suddenly wilt from root damage. Their tunnels are 2.0 to 3.5 inches across, in the top 4 to 18 inches of soil.
• Moles. 5 to 6 inches long, pointed snout, short tail. Tunnels show as raised ridges — but no mounds of soil and no plant-eating damage. Rabbits and deer leave smooth clips or jagged edges, and neither digs runways.

One free clue: hawks circling and diving over your yard is a classic vole sign. Coyotes, foxes, bobcats, weasels, snakes, and several owls and hawks eat voles.

3) Why the damage looks worst in spring — and what to do now

Voles do not hibernate. What changes in winter is that they stay under the snow, moving through grass runways where cover protects them from cold and predators. CSU Extension states that most damage occurs in winter, and that the greatest damage coincides with years of heavy snowfall. The reproduction numbers explain why a bad year feels sudden: three to six young per litter, three to 12 litters per year, and females that can become pregnant at three weeks of age.

CSU Extension is consistent on the method: habitat modification is the most successful and longest-lasting way to reduce vole damage, because high populations cannot establish themselves without food and cover. It is also the cheapest item here — mowing and weeding.

• Close-mow before the snow arrives. CSU specifically names close mowing in the fall before snow as a way to reduce vole damage to lawns. It removes the tall grass that serves as a safe haven, and voles avoid exposed areas.
• Cut the tall grass along fence lines, ditches and open space. CSU recommends mowing a swath of native grass along the fence line if you live near open space, to keep voles from crossing into your lawn. See our fall final-cut guide — a low cut late in the season is good practice anyway.
• Control weeds in the grassy borders. Weed ground cover is both habitat and food, and debris left in place prevents proper mowing.
• Trim mulch back from trees and shrubs, and shield the trunks. CSU's exclusion guidance is to encircle young trees and shrubs with 1/4-inch mesh hardware cloth or 3-inch diameter Vexar plastic-mesh cylinders, projecting 18 inches above the ground and 3 to 6 inches below the surface — the shielding we install on new plantings.
• Set traps now, if you plan to trap. CSU recommends mouse snap traps for small backyard populations, placed perpendicular to runways with the trigger end in the runway and baited with rolled oats or peanut butter. Trapping is the fastest way to reduce numbers.

4) Repairing the damage

Once the snow is gone, CSU Extension's guidance is short and specific: rake, fertilize and water the affected area. The lawn should recover once grass grows, though extensive areas may need reseeding.

• Rake out the runways. Break up the matted grass and fill the tunnels so seed and water reach the soil.
• Aerate before you seed. Vole tunnels compact the soil as they are built, and seed scattered onto compacted ground is the most common reason a repair "fails." Our aeration decision guide covers when it is worth it.
• Work the soil for good seed-to-soil contact. CSU is direct on this for vole damage: scattering seed over the damaged turf is ineffective. Work the soil, then seed.
• Fertilize and water consistently. A starter fertilizer at seeding plus steady moisture through the first few weeks is what closes the gap. Our lawn soil testing guide explains the sampling method CSU wants.
• Watch the window. The best overseeding window for a cool-season Front Range lawn is late summer into early fall — see our overseeding guide.

5) Trees and shrubs: damage you will not see until spring

The lawn damage is obvious. The more serious problem is above the lawn line. Voles gnaw on tree and shrub bark and can girdle the trunk entirely, killing the plant. CSU notes that trees which appear to suffer from disease or insect infestation may actually be suffering from unseen vole damage. CSU's own photo of vole damage on a lilac shows small, irregular tooth marks, all under the snow line — the girdling happens in the protected strip between the snow surface and the ground, invisible until the snow melts. If a juniper, rose, honeysuckle or young tree in your Johnstown or Berthoud yard girdles at the base over a winter, that is almost always voles, and the fix is forward-looking: guards around the base, mulch pulled back from the trunk, and tall grass and weeds cleared from the bed.

6) About poison: what we will and will not do

We are a lawn care company, not a pesticide applicator, so we do not apply rodenticide. Here is what CSU Extension says, because you should have it before buying anything.

• Two percent zinc phosphide is the most commonly used grain bait for voles in Colorado, and it is extremely toxic — keep it away from children, pets and wildlife.
• Timing is the whole ballgame. The best time to use zinc phosphide bait on lawns is during the fall before snow cover. Application in spring after the melt is usually ineffective.
• Secondary poisoning is real. CSU warns that rodenticides kill non-target species including raptors, dogs and cats, and that a pet can be poisoned by eating a poisoned vole. Anticoagulant baits take 5 to 15 days and should go in secure bait boxes.
• Fumigants do not work. Vole burrows are too shallow and complex for fumigation.

The sensible order is habitat modification first, traps second, and bait last — and never any of them without reading the label. We will do the mowing and the lawn repair, and tell you straight when the honest answer is that this needs a pest professional.