The common squirrel monkey has a head and body length that is 10.4 to 14.4 inches long. The tail length is 14 to 17 inches and the weight is 2.5 to 3.7 pounds. The tail is not prehensile.These diurnal monkeys are arboreal and only occasionally descend to the ground. Movement is quadrupedal with relatively little leaping. Ranges are often ill-defined and troops may number into the 40 to 50 range. During the mating season males establish a dominance hierarchy through fierce fighting with the higher-ranking individuals then interacting with the females. The females establish a dominance hierarchy during pregnancy. After the birth of the young, females exclude the males. The newborn cling to their mothers back for the first few weeks of life. Independence is achieved at 1 year.