The dominant female secretes a pheromone that suppresses ovulation in other females in the group. Callitrichids appear to have an estrous cycle as opposed to a menstrual cycle, as occurs in macaques. This cycle is approximately 15 days in most species. Callitrichids become sexually mature at approximately 16 to 25 months of age, however, copulation and masturbation may occur much earlier. The gestation period is approximately 150 days.
Tamarins usually give birth to twins.
Goeldi's marmosets usually have singletons. However, after several birth cycles, hand-raised callitrichids may care for their young. Breeders hand-raise marmosets in an effort to produce better pets. However, one must realize that these are wild animals and are not domesticated. Breeders remove infants from their parents for hand-rearing when they are between 3 and 10 days of age, so the infants can receive colostrum and milk for the antibodies.