Northern birch mouse is a tiny mouse-like animal. They are rusty-brownish, but have an easily noticeable black stripe on the back. One particularly characteristic feature is their exceptionally long tail. They live in humid forests with broad-leaved trees and shrubs. There, they look for slightly rotten stumps that has been left from falling trees, in which they build long burrows. In the burrows, they look for food. Additionally, the female builds a small chamber there for farrowing. They mostly eat all kinds of insects and their larva, but can also feed on seeds and buds. They are food for weasels and owls. They spend their winters in hibernation.