Within groups, the adult sex ratio of R. roxellana is heavily biased toward females, with a 5:1 ratio observed in some groups. This is consistent with the polygynous social organziation displayed by the monkeys. During the mating season, copulation is usually solicited by the female, who signals her estrus with proceptive behaviors, such as establishing eye contact with the male and then running a short distance away. The female also signals readiness via prostration, which involves lying with the head hanging down, the forearms stretched out or bent, the legs curled up, and the tail angling freely. Often, the prostrating female will point her anogenital region toward the male. The male responds initially with a wide opening of his mouth, and if he is interested (only about 50 percent of the time) he will mount the female. Ejaculation occurs in only a small percentage of the unions during the mating season (and it never occurs outside the mating season). For this reason, the sequence of solicitation and mounting between a male and a female may occur several times a day during the three-month mating period. Due to the scarcity of male ejaculate, a female may try to thwart the solicitation of another female to improve her chances for a successful copulation.

Mating System: polygynous

Golden monkeys display mating behavior throughout the year, but they breed on a seasonal basis, with all conceptions taking place within a three-month period. This period may start as early as August or as late as November, depending on the region where the monkeys live.

Once a female becomes pregnant, gestation lasts about seven months, with births occurring between April and August. Usually, one offspring is born.

(Kirckpatrick 1985, Ren et al. 1995, Schaller 1985)

Data are not available on many of the reproductive parameters of these monkeys. However, like-sized primate typically breed every year to two years, depending upon food availability. Weaning usually occurs around one year of age. In R. roxellana nursing may extend for a longer period because of the harsh climate which these animals occupy. Sexual maturity is reported to be at 4 to 5 years of age for females, and at 7 years for males.

Breeding interval: The interbirth interval of these animals is not known with certainty.

Breeding season: Golden monkeys breed between August and November.

Average number of offspring: 1.

Average gestation period: 7 months.

Range age at sexual or reproductive maturity (female): 4 to 5 years.

Average age at sexual or reproductive maturity (male): 7 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Mothers provide most of the care. Males have been observed grooming infants, however. Because of the social structure, which ensures that one male breeds with a group of several females, it is likely that this male, confident of his paternity, assists the females in some ways, by protecting offspring as well as by grooming them. In most primates, the period of dependence is fairly extended, and it is likely that this is the case for R. roxellana.

(Nowak, 1999)

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: Female, Protecting: Male, Female); extended period of juvenile learning