It is not observed that there is a certain season in which mating is more abundant. Yet, there is a birth peak that goes along with the time of year in which there is the greatest abundance of solid food. Colobus monkeys reach their sexual peak at 6 years in males, and 4 years in females. An adult female typically produces one young every 20 months and has a gestation period of 6 months. Both the male and female take care of the infants.
Tongue smaking by the female is usually the initiation of sexual behavior.
A group of colobus will average 8-15 monkeys, and usually has only one fully adult male and 3 or 4 females.