It is mainly an inhabitant of woodland and fields but is highly adaptable and can be found in most habitats if not too wet. They are rarely recorded on higher exposed ground with little cover. Wood mice are essentially nocturnal but some individuals may venture out in daylight.
They have dark brown fur with a white to pale grey underside, protruding eyes, large ears and a long tail. Head and body length (81-103mm); tail length (71-95mm); weight (13-27gms). The wood mouse and the yellow-necked mouse (Apodemus flavicollis) are easily confused, but the yellow-necked mouse is larger at about one and a half times the weight of a wood mouse and has a bright yellow chest spot joining the dark upper fur on either side of the neck.
Wood mice eat seeds, green plants, fruits and animal foods. In mixed deciduous woodland they eat acorns and sycamore seeds for most of the winter, buds in early spring, caterpillars, worms and centipedes in early summer, and blackberries and fungi in the autumn. Food is cached in underground burrows. Food remains are found in disused bird nests, on tree stumps and in sheltered feeding places between the roots of trees or under ledges. They tend to leave the flesh of fruit and eat only the pips.
Most wood mice live in underground burrows. The burrows are fairly complicated and may include nest chambers and food stores. Burrows probably survive from one generation to the next and will be enlarged or modified as required. Nests are commonly made of leaves, moss and grass. They are usually built below ground under the roots of shrubs or trees but are often found in buildings. Additional nesting material is used in autumn and winter and often the mouse blocks the entrance to the burrow with leaves, twigs or stones. Individuals will nest communally in the winter but in the spring females usually take up their own home ranges and nest singly. However, home ranges shared by two females have been observed. Breeding males range over larger areas occupied by a number of females. Litters of 4-7 young are born in successive pregnancies from March to October but autumn litters are small. The young are born blind (eyes closed) and hairless. They are weaned at 18-22 days of age when their weight is about 6-8 grams. Growth in the summer is rapid and females can become pregnant when they have reached a weight of 12 grams. Breeding may continue over the winter if a good food supply, such as a heavy acorn crop, is available. Few adults survive from one summer to the next. Their predators include foxes, weasels, owls and domestic cats.
Wood mice can often become pests of stored food in buildings and will take bulbs, beans, peas and tomatoes from the garden. Minor losses to forestry and agriculture due to wood mouse feeding can be ignored when balanced against the consumption of weed seeds and invertebrate pests. It is extremely common for many properties in rural settings, both commercial and residential, to experience regular seasonal problems of invasion by this species. Wood mice have no legal protection and conservation does not seem necessary as recolonisation after mortality is often rapid. Wood mice can be beneficial to man by preying on harmful insects and many trees and shrubs germinate from forgotten wood mouse food stores.