As a result, under ideal conditions vole populations can reach densities as high as 270 voles per acre. Scientists have found that voles exhibit regular population fluctuations at approximately 4-year intervals. Populations apparently crash to levels as low as 10 voles per acre after peak years and then begin to build up again. Extensive damage may occur in orchards, particularly during peak population years. Damage Voles may cause extensive damage to fruit trees and orchards as a result of girdling seedlings and trees and damaging roots.
Damage occurs primarily during winter when other types of food are scarce.
The most common form of tree injury caused by meadow voles is trunk girdling at or near the ground surface. Since voles burrow in the snow, they may damage tree trunks as high as snow accumulates. Young trees are especially susceptible to attack. Damage from pine voles is harder to detect, because it occurs underground as voles consume small roots, girdle large roots, and eat bark from the base of trees. By the time orchardists note weak, unhealthy trees, the damage is already extensive.