There apparently are both aquatic and nonaquatic populations of these voles. The aquatic populations, which include most A. terrestris in the western parts of Europe, live along the banks of streams, ponds, and canals, where the water level is constant. They dive freely and swim either on the surface or underwater, sometimes near the bottom of the pool or stream, where they enter burrows that terminate below water level. These populations occupy grasslands and cultivated areas, construct extensive burrow systems, and leave conspicuous mounds on the surface. The burrows average 40.2 meters in length, contain one or two nests, and in autumn and winter contain storage chambers.
Bank voles are either nocturnal or diurnal and are active throughout the year.
They feed on aquatic plants, herbs, grasses, twigs, buds, roots, bulbs, and fallen fruit. Some food is usually stored for the winter, though the animals continue to forage at this time. Although water voles are sometimes found under crowded conditions, they do not form large social groups. Females also fight each other, but not to the same extent as males. These populations usually breed from March to October, but winter reproduction is not unusual.