The genus is second only to gibbons in being the most agile in trees, using their long tail as a fifth limb. They form troops of from 2 to 30 monkeys that tend to frequently break up and rejoin. There are only a few males in a group. They are not leaf eaters. Life Cycle and Young Squirrel monkey females become sexually mature at approximately two and a half years old.
Males become sexually mature at four years old.
The gestation is about one hundred and forty-two days. The baby clings to the back of the mother from birth. The father of the baby squirrel monkey doesn't help in raising the young, but other mothers with new young will. Squirrel monkeys give birth to only one monkey. The weight of the infant is about 112 grams for the males, and 106 grams for females.