Vole damage to trees: gnawing at the soil line, as extension services describe it

This page reports what the official source says. It is not legal advice: ask the office named here. Rules on controlling voles differ by place, and the University of California note below describes one state's wildlife code, administered by the California Department of Fish and Wildlife. The page describes what the sources say the damage looks like and the guards they list. It does not say what to do about any tree or animal, and baits are mentioned only as the sources name them. For protected species and nests in tree work, see the guide on wildlife and the law.

What the damage looks like

UC IPM's Pest Note on voles (publication 7439, revised April 2025) says vole damage to trunks normally runs from a few inches above the ground to a few inches below, so soil may have to be pulled back to see it. It describes gnaw marks about 1/8 inch wide and 3/8 inch long, in irregular patches and at various angles, with droppings, runways and burrows as other signs. The University of Kentucky Extension workbook for Christmas tree plantations says vole gnawing is told from rabbit damage by the lack of uniformity of the marks and by the place on the tree, near the base, and that tracks, droppings and burrow systems should confirm it. South Dakota's forest health update of February 5, 2020 puts the difference at the position above ground and the bite size: voles have very small teeth and leave small irregular marks, where rabbits leave marks about 1/4 inch wide.

Purdue University and the USDA Forest Service (FNR-216, hardwood plantations) describe two species that harm trees in the Midwest. The meadow vole lives in wet meadows and grasslands and builds surface runways about 1.5 inches wide. The pine vole lives in forests, old fields and orchards, leaves small conical piles of soil at burrow openings and does not use surface runways. They say voles switch from grasses to bark in fall and winter and may girdle larger roots underground. Kentucky says pine voles attack trees of all sizes in every season, with most of their damage below ground on rootlets and the bark of larger roots. Iowa State University Extension says meadow voles may eat the bark of small trees and shrubs in winter, and that mice and other small rodents can chew bark where straw or leaf mulch gives them cover over winter.

Whether the sources call it harmful

UC IPM says girdling damage on trunks and roots can kill trees. It lists signs of partial girdling: a long wait for young trees to bear fruit, reduced yield, abnormal yellowish leaves and poor vigor. It adds that with snow cover damage can extend a foot or more up the trunk and that damage beneath snow often goes unnoticed until it is too late. Purdue says injured trees look weak, grow slowly and appear pale, and that by the time they look unhealthy the root damage is already extensive. Purdue also reports population swings every 2 to 5 years; UC IPM reports some populations peaking every 3 to 6 years.

Look-alikes

UC IPM names pocket gophers as another animal that girdles trunks. It says vole girdling generally occurs above ground and gopher girdling below ground, and that open burrow entrances versus closed gopher mounds can help tell them apart. Rabbit damage, with wider marks higher on the trunk and clean slanted cuts on twigs, is on the rabbit damage page. Deer damage is on the deer damage page.

Guards the sources list

UC IPM lists cylinders of hardware cloth, sheet metal or heavy plastic around the trunk, fences or flashing with fine mesh, and a ring cleared of vegetation around young trees, since voles prefer not to feed in the open. Iowa State lists hardware cloth cylinders and keeping wood mulch away from small trunks. South Dakota names removing ground cover and hiding cover as the best means of managing voles, and says trapping is not effective for protecting a long windbreak. Purdue and the Forest Service mention tree shelters and guards, and describe poison baits as restricted-use pesticides that must be applied by a licensed, certified applicator. Who holds such a licence is covered in the guide on pesticide licences by country.

UC IPM adds that the California Fish and Game Code classes voles as nongame mammals and that an owner or tenant has permission to control them when they injure or threaten crops or property. Other places have their own rules. The group is listed on wildlife damage to trees.