These large squirrels are very colorful mammals, and coloration varies widely. The underparts are buffy to white. Fading and the growth of new hair in well-defined areas often produce the effect of colored patches on the back, which are not true differences in pattern. The ears are short, round, and in R. macroura they are tufted. The hand is very broad, the inner paw is expanded for gripping, the feet are broad, and the claws are large and powerful.
Females have three pairs of mammae.
These squirrels are arboreal, usually going to the ground only to chase another squirrel or to follow a female during the breeding season. They are extremely agile in the trees, making leaps of six meters or more and progressing rapidly through the treetops. Holes in trees are used for shelter. During the breeding season a large globular nest about the size of an eagle's nest is constructed in tree branches. The young are born and raised in this nest.