The basic life cycle of a monkey is gestation, babyhood and adulthood, but the length of each of these steps varies based on the type of monkey being described. Monkey gestation can take four to eight months, and monkeys take 18 months to 8 years to reach maturity. After breeding, mature monkeys give birth to one to three babies with one being the most common number.
A snow monkey has a fairly typical life cycle for a monkey. They are born after a short gestation period, and they nurse for about a year. Snow monkeys become adults at age 4, and in captivity, they live up to 30 years.
Some monkeys experience an adolescent phase between being a baby and an adult. For example, the Proboscis monkey stops nursing at seven months old. About five months later when they are 1 year old, young males leave their mothers to hang out with their friends in a group called the bachelor group. Young females, in contrast, stay with the rest of their family in a group called the troop. Although the monkeys are not considered babies during this period, they are not adults either. They spend roughly three years in this role, and they are not ready to breed until they are 4 or 5.