Their peak activity times are at dawn and the late afternoon. In the northern part of their range, red squirrels often spend the winter in a system of underground tunnels. They are very vocal and loudly scold intruders in their home range.
Vocalizations consist of rattles, screeches, growls, buzzes, and chirps.
Red squirrels often migrate if their local food supply runs low. During these migrations they will often cross water and are good swimmers. They are a major prey item for other economically important species such as martens, bobcats, and lynx. The dorsal coat is usually brownish or olive-red in color. During the summer, a black stripe can be seen on the side.