After ground squirrels, the other problem rodents I deal with yearly are voles, otherwise known as meadow mice.
The first signs of these destructive critters are golf ball-size holes that are the entrances to their underground tunnels. There are dozens of holes throughout our yard in the lawn, flower and shrub beds. Voles also make shallow, cut-grass covered runways through the lawn. These runways connect many shallow burrows.
Unfortunately, voles are active year-round, breed year-round (five to 10 litters per year with three to six young each litter) and often do significant damage to woody plants from under the snow.
According to the University of California, Davis Integrated Pest Management program, “several adults and young can occupy a burrow system.” A system may be a few hundred square feet in size. Populations fluctuate year to year. A vole lives about one year.
Voles eat a broad variety of plants and plant parts including grasses, flowers, vegetables, tubers, bulbs, bark above and belowground, and roots of trees and shrubs. If you have junipers, you may now be noticing dead or dying branches that indicate where voles have eaten the bark and inner tissue killing the branch. Look for gnaw marks.
Prevention is, as they say, worth a pound of cure. Populations must be controlled before they get large. Removing the vegetation, grass clippings, mulch or leaves they hide under is one way to reduce their numbers. I have raked our beds exposing the bare ground, so the hawks and neighbor cats can get at the voles. We should have mowed the lawn much shorter in the fall, which would have eliminated long grass to hide in.
UCDIPM says to keep areas around tree trunks free of mulch, grass or ground covers for four feet, because voles don’t like open areas. To protect gardens, put fences around them with ¼-inch mesh or smaller, at least 12 inches tall and buried six to 10 inches deep. Wrap or cover ornamentals with hardware cloth, sheet metal or heavy plastic for protection. Be sure there is space between the material and the trunk to allow for trunk growth.
Mouse traps placed at right angles across runways help. You may need a dozen or so for a small garden and up to 50 for a large area (UCDIPM). They trigger the trap as they run through. Empty them of dead rodents and reset them daily. Keep trapping until you stop catching them there and then move the traps to another location.
Since voles may carry infectious diseases, don’t handle them without rubber gloves. Bag them in plastic and put them in the trash. Pest management is a never-ending battle.
For information: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7439.htm