Home / Blogs / Voles: The Tree Planter’s Worst (and Cutest) Enemy
July 10, 2023
Woodland vole (microtus pinetorum) (Photo credit: Mammals of North Carolina website)
I don’t think anyone would argue with the fact that tree planting is a crucial part of watershed and forest restoration. These plantings help stabilize eroding stream banks, prevent runoff that pollutes our waterways, and provide more habitat for native species. Here in the Pennsylvania office of the Alliance for the Chesapeake Bay, riparian buffer and forest maintenance is a large part of our conservation efforts for the Chesapeake Bay watershed. The sites where these trees are planted can vary greatly from old agricultural fields to rocky hillsides to moist streambanks where many different plant and animal species can be found. Moles and shrews can be two common species to see in these areas, running across your feet in search of grubs and other insects to feast on. These are generally of no concern to the average landowner, however, one particularly herbivorous species can be found in almost every type of planting site and consistently proves to be a nuisance: voles.
Meadow vole (microtus pennsylvanicus) (Image from the Chesapeake Bay Program).
In Pennsylvania (particularly the southeast region) there are two prominent species of voles that can play a significant role in the survival rate of trees and shrubs. They create tunnel systems through yards, fields, and streambanks, creating nests and searching for food, causing irreversible damage to young trees in the process. The meadow vole prefers to stay above ground on the surface and use leaf litter or tall vegetation for protection from predators. These tiny mouse-like critters favor moist fields with thick grasses and weeds but typically avoid forests. In the winter when grasses, sedges, and other leafy vegetation is hard to come by, voles turn to trees and tree bark for their needed nutrients. They chew on the bottom of the trunk, which usually results in girdling of the tree and even mortality.
The woodland vole (sometimes called the pine vole) is more akin to a mole than a mouse like its close relative, the meadow vole. Woodland voles burrow into the ground just below the surface, disrupting and loosening the soil to create their elaborate system of tunnels. This not only makes the soil unstable, it also gives them direct access to the roots of trees and other vegetation. With the meadow vole eating the bark and the woodland vole chewing on the roots, these young, defenseless trees are being attacked from all sides!
Woodland vole (microtus pinetorum) (Photo credit: Mammals of North Carolina website).
While there are a number of other animal species likely to cause harm to young trees in buffers and other areas, such as rabbits or groundhogs, vole damage is identifiable by the paths they create in the surrounding grasses. They also sometimes leave identifiable bite marks on trunks and limbs of trees, with a haphazard pattern made by noticeably small teeth.
Vole damage to a young tree (Photo credit: Sarah Lang)
Undoubtedly, the question that first comes to anyone’s mind when discovering this damage must be, “What do I do about it?” Voles are notoriously social creatures, so if one is discovered, it is likely that there are more nearby. These voles are native to this region, so the best approach is to protect the trees from them until the trees are well established. At the Alliance, each tree we plant is guarded with a tree shelter that not only protects the trees from animal browse and herbicides, but also promotes healthy growth by providing a greenhouse effect with its translucent material. The shelters are pushed down into the ground (roughly 1-2 inches) to protect the tree’s roots. Call that hitting two birds (or voles?) with one stone!
I find it pretty incredible how such a small, adorable, innocent-looking creature can cause such irreversible damage. It is because of unsuspected pests like these that general maintenance and upkeep of a freshly planted area must be completed, at least until the trees are old enough to survive potential damage. Not only will the use of tree shelters aid in protection, but annual to bi-annual mowing and herbicide applications will ensure that a healthy, happy forest is created.
Written by: Sarah Lang, 2023 Summer Pennsylvania Forests Intern
Forests for the Bay