It weighs about 28 grams. The total length of the body from head to tail ranges from 11 to 20 cm. The ears are quite large and are covered with fine hairs. The deer mouse is an omnivore. Its' diet is mostly seeds and fruits.
Insects also are an important food source.
Raspberries, blackberries, blueberries, elderberries, spiders, and beetles are among some common items on its' daily menu. The deer mouse, itself, is a source of food for many animals. Some predators of the deer mouse are owls, weasels, foxes, snakes, skunks, minks, raccoons, bears, coyotes, and wolves. Only about five percent of the babies born live past the first year of life. The number of litters that each female has varies from year to year.