Squirrel monkeys and capuchins generally have a promiscuous mating system, with both males and females mating with multiple individuals. Capuchin females solicit mating from multiple males, including the group's dominant male, making paternity difficult to determine. Males do not compete for access to females.
Marmosets and tamarins are characterized by monogamy or polyandry, with each social group having a single, dominant, breeding female. These dominant females either breed with a single male or with multiple males. Gould's marmosets are the exception, with multiple breeding females present in social groups. Other marmoset and tamarin species have been reported to have multiple breeding females, but these are generally the daughters of the dominant female, and they have much lower reproductive success.
Cebid parents generally have help from other members of their social group in raising offspring.
Mating System: monogamous ; polyandrous ; polygynandrous (promiscuous) ; cooperative breeder
Squirrel monkeys and capuchins give birth to a single offspring each year and species may be seasonal breeders, often with breeding during the wet season when food is abundant, or species may breed throughout the year. Gestation is 155 to 180 days in squirrels monkeys and 149 to 168 days in capuchins. Females have estrus cycles during the breeding season that vary from 12 to 18 days in length. Male squirrel monkeys change their morphology during the breeding season, gaining a substantial amount of weight in their upper body. Males in this breeding condition are called "fatted" males.
Marmosets and tamarins give birth mainly to dizygotic twins, although single births and triplets are also reported. They give birth once yearly during a breeding season that corresponds with the local wet season. Births occur at night. In captivity births occur twice a year, but this is rarely observed in the wild. The exception to this pattern are Goeld's marmosets, which give birth to a single young during the wet season, although births may occur year-round in captivity. Gestation length is from 129 to 183 days.
Squirrel monkey females reach sexual maturity at 3 years old, males at 5 to 6 years. Capuchin females become sexually mature at 4 to 5 years, males at 8 to 10 years. Marmosets and tamarins reach sexual maturity at 12 to 24 months old.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
In squirrel monkeys, females care for their young almost constantly for several months after birth. At 3 to 4 weeks old she may allow other mature females with young to carry her young, but she will maintain visual contact at all times. Juvenile females may also be allowed to briefly carry the young. Young are weaned at 5 months and become independent at 11 to 12 months, just before the mother gives birth to her next infant. Even after independence, young squirrel monkeys stay close to their mother and travel with her.
Capuchin young also rely almost entirely on their mother for care. They are carried on the mother's underside for the first 6 weeks of life, after which they switch to riding on her back. Capuchin young nurse for several months and other members of the group will come to assist young capuchins if they become distressed. Both capuchins and squirrel monkeys remain close to their mother, but begin to explore their environment at about 2 to 3 months old, including playing with similarly aged individuals.
Marmoset and tamarin females give birth to young with one of the largest body masses, relative to female body mass, of all mammals. The combined birth weight of twins is 20% of maternal body mass, only tarsiers have higher ratios of infant to maternal body mass. This large investment by females in young before their birth is offset by extensive parental investment by males after the young are born. Male tamarins care for young from birth, carrying and protecting them. They return the young to their mother for nursing occasionally. Marmosets and lion tamarins share infant care among all group members and Goeld's marmoset females carry their young until about the second week of life, when all group members begin to help. Carrying such large offspring is a significant energy burden. Even captive tamarin males lose up to 10% of their body mass in the first few weeks of caring for newborn young. Wild tamarins that have to travel to search for food are likely to experience much larger stresses. Young marmosets and tamarins are weaned at about 3 months old. Group care extends to communal feeding of young as well, young emit a chattering or squawking vocalization that prompts group members to give up food items.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning; maternal position in the dominance hierarchy affects status of young