Meadow voles create surface runways in the grass, and in winter, they are active in these runways beneath the snow. Pine voles build underground tunnels in loose, crumbly soil. As they build the tunnels they push out dirt, producing small conical piles of soil on the ground surface. Both voles build large globular nests of dry grasses and leaves. The nests are located close to tree trunks, in tussocks of grass, and at the end of burrows.
Voles are extremely prolific.
Their peak breeding activity occurs between March and October, but when winters are mild, voles may breed all year long. A female meadow vole could potentially produce over 70 young in a year, and the young voles become sexually mature at the age of 1 month. 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.