As the weather warms and we are spending time outside while practicing physical distancing (I like this better than social), we may be noticing “raceways” or small holes in lawns, grassy areas, natural areas and pastures. These pathways are not caused by a disease but by voles, a mouse like rodent. Voles are similar to mice but have stockier bodies, a less pointed nose, short legs and a shorter tail. They nest underground under trees and shrubs. In years when we have snow cover that stays for a longer time, we tend to see more damage. Voles travel along the “raceways” under the snow finding food and avoiding their predators.
The damage you might notice is dead young trees, perennials or shrubs. Voles girdle the bark of young trees, shrub branches and damage perennial roots. If you notice young trees or shrub branches that have died, check for girdling at the base or damaged roots. You will see chewed bark or roots on the plants made by their small teeth. Grasses will recover from the damage, but a completely girdled tree trunk, branch or roots will not.
The two most effective management methods are habitat modification and exclusion. Habitat modification for turf grass areas is mowing the grass shorter in the fall to reduce protection for the voles from predators. They like to nest under junipers and other shrubs so removing lower ground lying limbs enable a fox, coyote or cat to get under the plant can help reduce the vole population. Within a home landscape, you need to identify your plants of highest value and protect them. Young trees, shrubs and perennials are prime targets. You can exclude voles by using hardware cloth (heavy duty screen with openings less than ¼”) or other commercially available tree guard. Bury the guard a few inches into the ground or secure it to the ground. The guard should be 12 to 18”, higher to account for snowpack. Guards will also protect plants from rabbits if it extends beyond the snow pack and the rabbit’s reach.
You can try using repellants, toxicants or trapping. Repellants such as Thiram® (a fungicide) or those containing capsaicin (the heat in hot peppers) are the most effective. There is research that Milorganite®, a fertilizer made from processed sewage is showing effectiveness against voles and rabbits. It has been processed at 1600 degrees, so it is safe. The problem with repellants is that they must be reapplied periodically and that voles can get accustomed to them over time. Follow the label for application instructions and re-application timing. Changing the repellant active ingredient periodically can help prevent voles from adjusting to the repellant. Toxicants and traps can be used but you need to be careful so that you do not trap or poison other animals. Standard mouse traps can be used for voles if placed end to end in the “raceway”. They need to be installed under shrubs or under a piece of gutter where you see their holes or along their “raceways”.
If you live on a small acreage, you can install perches for raptors to help lower your population. If you live near a park or open space, there’s not a lot you can do other than protect your plants. The open area will just be a breeding ground for all those hungry voles just waiting to make a meal of your favorite plants.
By Sharon Bokan, Colorado State University Extension – Boulder County. For more information on dealing with voles, check out “Managing Voles in Colorado” Fact Sheet #6.507, visit extension.colostate.edu/topic-areas/natural-resources/managing-voles-in-colorado-6-507. For assistance with other wildlife conflicts, contact the Colorado State University Extension Boulder County Wildlife Master volunteers by calling 303.678.6238 to leave a message. Volunteers check the voice mailbox daily.