Due to the limited number of longitudinal studies on black uakaris, little is known about their mating behavior. Generally, Cacajao species live in large multimale - multifemale groups. These groups range from twenty to over a hundred individuals, making it possible that there are competitive mating strategies and that social hierarchy plays a role in mating opportunities. However, the lack of the major markers of sexual dimorphism such as large male canine size, the presence of sagittal or nuchal crests, or flamboyant colorings suggests that this species is largely monogamous, as is its sister taxon Cacajao calvus.
Breeding appears to be seasonal, as young infants and lactating females have been observed only in the months of March and April, corresponding with the setting of fruit in igapo forests. Females give birth to single offspring. Infants receive care for some months, including being carried on the backs of parents in the months of June and July, when water levels are at their highest. Black uakaris have never successfully bred in captivity, so little is known of the specifics of breeding season or interval, gestation, or the development of infants and juveniles. In the more well-studied sister taxon C. calvus, the age of sexual maturity for females is approximately 43 months, with first pregnancy occurring soon thereafter. The offspring of C. calvus are weaned after approximately 550 days. The adult body size of C. melanocephalus is slightly smaller than that of C. calvus, thus the lengths of time for these life-history features in C. melanocephalus may be somewhat shorter.
Breeding interval: Breeding intervals are not known in black uakaris.
Breeding season: Breeding appears to be seasonal, as young infants and lactating females have been observed in the months of March and April.
Range number of offspring: 1 (high) .
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Average number of offspring: 1.
A typical primate trait is extended postnatal care of young. This has also been observed in black uakaris, where adults carry infants on their backs during the months of June and July when flood waters are particularly high. Little is known of the specifics of C. melanocephalus parental investment, as they have never bred in captivity and there is limited longitudinal data on this species. However, C. calvus exhibits extended parental care, including long term lactation.
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 (Protecting: Male, Female); extended period of juvenile learning