The northern birch mouse is a small rodent with a slender body and a long tail. It is most active around the start and end of the night and hibernates underground in winter.
Its upper fur is reddish brown, with a dark stripe running from head to tail; its underside is pale gray-yellow. The flexible tail is longer than the body and helps it grasp and balance. In young animals, the stripe may be faint during their first summer.
It moves around the beginning and end of the night, climbing through shrubs, ferns and grass stems. It is active in the warm part of the year and hibernates in a burrow during winter.
A tracking study in Denmark found that the mice used hedges and ungrazed grassland more than grazed grassland or fields. Activity was higher during the spring mating season and fell as hibernation approached.
An extinction-risk assessment has not been added yet.