A deer mouse can be identified by its long, triangular nose and large, black eyes. The deer mouse is often brown in color, while a common house mouse is typically gray.
The top of the deer mouse ranges from brown to reddish, and the belly of the mouse is white. The deer mouse has large, rounded ears with sparse fur. Deer mice have long tails that are reddish or brown on top and white on the bottom. Common mice have a darkly colored, hairless tail that is typically uniform in color. Deer mice may also be gray and white, rather than reddish or brown, depending on the region where the mouse lives. Both gray and brown deer mice feature a white underbelly and bi-colored tail.
Mature house mice are larger than deer mice. The typical size of a mature deer mouse is about 4 inches, or 7 inches including the tail. A common mouse reaches up to 8 inches in length.
The back feet of deer mice are often smaller than common house mice. Additionally, the separation of colors on deer mice is sharply noticeable, while a common mouse has colors that blend together gradually. The color differences between deer mice and house mice are particularly distinguishable when examining tails.