Over several decades of experience with biology and gardening pursuits, surprisingly, I have not had much contact with burrowing mammals – not until 2009, that is. On September 1, 2008, Hurricane Gustav – at that point a Category 2 hurricane – roared into my hometown of Baton Rouge, Louisiana, inflicting significant damage to the area’s extensive tree cover. My property was not spared. Although my house escaped severe damage, 18 of my large trees (mostly oaks) that were primarily in my half-acre side yard were either toppled or so severely damaged that they had to be removed. My previously shaded landscape was now bathed in strong sunlight. The following spring, weeds invaded with a vengeance. By autumn, I had to employ a rotary cutter to avoid the wrath of neighbors.
Enter moles and voles. Once the temperatures cooled in early winter, I noticed that when I walked about my half-acre, my feet sank an inch or so – as if I were walking on a sponge. Upon close inspection, I noticed that much of the topsoil had been pushed up into low ridges indicative of something burrowing beneath. These ridges zigzagged erratically throughout my yard. I concluded that it was tunnels that were collapsing beneath my feet. Then one morning, I happened across a small furry animal dead on my sidewalk. The corpse had a peculiarly shaped oversized nose. From a field guide, I was able to ID it as a star-nosed mole. At that moment, I decided to begin a new research project.
Moles and their lesser-known co-conspirators, voles, share several characteristics. To begin, both are viewed as pests, aka varmints or vermin. They infest gardens and lawns of homeowners, fields of farmers, and pastures of ranchers. Both are warm-blooded mammals covered with hair and produce live young, which are nurtured on milk produced by mammary glands. Both are small, averaging about 4 to 6 inches in length. Their mini-pelts are velvety, and may be brown, gray or black. In addition, both have relatively stocky bodies that they can flatten, short legs and tails, tiny eyes and poor vision, long claws for digging, and barely visible external ears – all adaptations to life in dark, cramped, subterranean spaces. When alarmed, the little guys can make a high-pitched squeak, though. Both are timid, secretive, and nonsocial, living from three to five years singly, just below ground in small dens that are connected to tunnels or runways that they use in search for food. The animals can dig as much as 90 to 100 feet per day.
While these fuzzy, miniature bulldozers are nearly impossible to observe, their presence cannot be overlooked: slightly raised dirt ridges that meander through lawn or garden. When a tunnel impacts the footing of, say, a sidewalk or driveway, the tunnel will then skirt the structure as a dirt levee. And not to be dismissed is the fact that both moles and voles are capable of transmitting diseases (rabies for example) to humans. But because of the animals’ subterranean lifestyle, the incidence of disease is very low. Nevertheless, moles and voles should not be candidates for pets. Similarities end there, though.
Taxonomically, moles and voles exhibit poignant anatomical differences. But for the layperson, there are more obvious contrasts. In particular, moles belong to a group of mammals called insectivores. Members hunt and feed on small animals, especially insects – both adults and larval grubs – and earthworms, consuming up to 100 percent of their body weight each day. The closest relatives of moles are shrews, hedgehogs and bats.
Confounding matters is the fact that the word “shrew” is more familiar to most Americans than “vole” – recall Shakespeare’s classic The Taming of the Shrew. In reality, shrews resemble a long-nosed mouse, are 2 to 4 inches in length, and possess spikelike teeth. They don’t burrow on their own, but haunt the runways of moles and voles in search of small prey, which they dispatch with infamous viciousness.
Within the U.S., common species of mole include: eastern mole, western American mole, and star-nosed mole. The entrances to their sub-surface dens are bordered by a small mound of dirt, a dead giveaway for mole rather than vole. These entrances, however, can be difficult to observe because they are often concealed under piles of logs, brush and rocks.
On the other hand, voles, which are sometimes referred to as meadow mice, belong to a large assemblage classified as rodents. This lineage includes beavers, chipmunks, gophers, lemmings, marmots, nutria, mice, porcupine, rats, squirrels – and those cute house pets marketed as guinea pigs, hamsters and jerboas.
Voles resemble small, stocky mice with slightly rounded heads and short, hairy tails. Their claws are less pronounced than those of moles. As with all rodents, voles are extremely fecund, producing five to 10 litters, each made up of two to five young. Their subterranean runways are visible as raised ridges punctuated with small openings that lack adjacent mounds, probably because voles sometimes nest aboveground under brush. Voles are vegetarians, not hunters, and are equipped with oversized incisors for their gnawing habit.
These animals will munch above ground on grass, tender bark of saplings, seeds and nuts. Voles, however, are partial to the roots of plants. Unfortunately for us, this includes flower bulbs and food tubers, including potatoes, carrots and beets. Common species in North America are the meadow vole, pine vole, and mountain vole.
That moles and voles can cause both physical and cosmetic damage to lawns and gardens is a no-brainer. But unseen tunnels can be treacherous, too, in that they can trip us, our livestock, and our pets. Both humans and horses, for example, have been known to fall and break a leg after stumbling into a collapsing runway or den.
What to do
The answer is not simple. Lucky for us, both moles and voles are hypersensitive to odors and vibrations. Any substance that emits strong vapors can act as a repellent for most burrowing animals. Over the years, homeowners have inserted into runways various odiferous compounds. The list is long: moth balls and flakes, rags soaked with gasoline, ground cayenne pepper, pepper sauce, castor oil, garlic, Clorox, vinegar, ammonia, soiled kitty litter, Epsom salt crystals, and even smoke bombs. Likewise, many pest control companies market their own brand of mole-vole repellents. These are usually pellets or crystals that contain castor oil, fox urine, and the toxic chemicals bromethalin and zinc phosphide. One company even markets toxic bait in a clever wormlike impersonator –
I kid you not! And if that’s not enough, a few entrepreneurs produce devices that thump the ground or generate ultrasonics created by small windmills.
But before you rush to your pantry or nearest home improvement center, consider this: All pest deterrents have restricted zones and limited times for effectiveness. That means that when a given runway becomes unattractive, the offending animals will usually construct new tunnels, and these may or may not be off your property. Then, as soon as the intrusion disappears, the animals often return to their former arenas. And don’t forget that some of these chemicals can cause temporary or permanent harm not only to pests, but to humans, pets and vegetation, as well as to beneficial soil organisms.
Most experts suggest that if you have a serious mole or vole infestation, you should first try passive measures that discourage these animals. Consider purchasing a dog (terriers are noted for their high prey drive) or cat (house cats will hunt moles for play and food). Other suggestions include removing brush piles, encircling your small trees with wire mesh or cloth, not placing mulch for your trees in direct contact with the trees’ bark, reducing ground covers, regularly flattening the ridges above tunnels by using your feet, and watering the infested territory as often as possible. Water causes tunnels to collapse and moistens the soil so grubs and plant bulbs can’t thrive.
If problems persist, you may want to contact a pest control company to set traps, or else personally purchase traps marketed by many home improvement enterprises. The hapless animals are either killed outright or contained so they can be later relocated. Some experts suggest that the only humane way to deal with moles is to use traps that dispatch the animals immediately.
The good with the bad
Moles and voles are not all bad, though. These small mammals are doing only what they are designed to do as part of natural food webs that operate within ecosystems. Take burrowing. By its very physical nature, burrowing churns soil. The physical activity mixes inorganic and organic nutrients and introduces fresh air and fresh nutrients from the animals’ excretory products, all of which boost plant health. Remember, too, that because moles are voracious feeders, they can seriously reduce the number of beetle grubs and other pests, some of which not only damage the roots of plants but spread harmful viruses to urban trees. And lastly, moles and voles are important food items for animals higher on the food chain: owls, hawks, foxes, raccoons, bobcats and coyotes, to name a few. Because humankind is now an ever-present and inherent force of nature, wildlife of all types and sizes is vanishing at breakneck speed. You may wish to alter your thinking to embrace a mantra of ecological stewardship.
Or, if your yard or meadows are rife with the pests and their damage, take action as outlined above. Reducing numbers can go a long way toward making the impact far less noticeable.
Meanwhile, I concluded that my personal turf in 2009 was besieged by both moles and voles. I theorize that the pests were responding to the rampant vegetation and insects that invaded due to sunlight from my venue’s new open canopy. Over the years, I’ve done little to discourage the small mammals, other than use my feet to collapse tunnels to restore a copacetic look to my lawn. As a reward, tunneling in my yard is now minimal. Looks like my subterranean nuisances and I have struck a truce – I can live with that.
A retired professor of entomology and award-winning nature writer, Dr. Gary Ross enjoys directing butterfly festivals for the North American Butterfly Association and exploring the swamps and marshes of his native Louisiana to research and photograph unusual aspects of nature.