Courtship is a very important part of reproduction in Japanese macaques. Japanese macaques spend on average 1.6 days with their potential mate during courtship. During this time, they feed, nest, and travel together. Females stay with higher ranking males longer than with lower ranking males. When high ranking males observe a low ranking male with a potential mate, they may try to disrupt their courtship. Copulation can occur arboreally or terrestrially. Females have two types of mating calls. The first is a squawk or squeak that is vocalized just before copulation. The second sounds like an atonal cackle and is vocalized after copulation. Japanese macaques are polygynandrous; males and females copulate with available individuals and have multiple partners during a breeding season.
Mating System: polygynandrous (promiscuous)
Female Japanese macaques reach sexual maturity around 3.5 years of age, while males reach sexual maturity around 4.5 years. Although males as young as 1.5 years of age have been observed mounting females, they do not successfully copulate until they are older. Breeding usually occurs between March and September. Gestation lasts an average of 171.7 days, although this is misleading; adding one standard deviation in either direction produces a range of 157 to 188.5 days with a 95% confidence level. When females are ready to give birth, they usually leave the troop and find a safe and private place. Japanese macaques generally have 1 offspring during a breeding season. Twins are rare and occur once in every 488 births. At birth, males weigh on average 539.7 g and females 548.8 g. Weaning may occur as early as 6 to 8 months in some Japanese macaques. In some special cases, however, mothers may continue to nurse their offspring for up to 2.5 years if they have no other intervening births. Female Japanese macaques can produce a perfectly viable infant up to 25 years of age, although this is usual. Fertility does not appear to be correlated with menopause.
Some female Japanese macaques have been observed carrying the body of their infant that was stillborn or otherwise killed, such as in an attack by raccoons or dogs. This behavior sometimes lasts for several days. Males have also been observed committing infanticide. This may reduce time before a female is able to reproduce again, giving the male an opportunity to reproduce.
Breeding interval: Japanese macaques can breed once a year.
Breeding season: Japanese macaques breed from September to April
Average number of offspring: 1.
Range gestation period: 5 to 6 minutes.
Average birth mass: male 539.7 g; female 548.8 g.
Range weaning age: 6 to 24 + months.
Average age at sexual or reproductive maturity (female): 3.5 years.
Average age at sexual or reproductive maturity (male): 4.5 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous
Average birth mass: 496 g.
Average number of offspring: 1.5.
Average age at sexual or reproductive maturity (male)
Sex: male: 1369 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 1483 days.
Parental care is an important aspect of the growth of Japanese macaques, and infant mortality is high in this species. Mortality before 1 year of age is 28.4%. During the first 4 weeks of life, infants are carried near the abdomen of adults. Young are carried near the abdomen or on the dorsal side of adults until they are 1 year old. Female Japanese macaques groom their adult offspring more often than their juvenile offspring. This may occur during the time frame when offspring observe behavioral patterns of their mothers, learning multiple successful traits needed later in life. In some troops of Japanese macaques, male paternal parental care is also present. Occasionally males, even high-ranking males, have been observed grooming and protecting infants. Males also carry infants from time to time.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Male, Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning; inherits maternal/paternal territory; maternal position in the dominance hierarchy affects status of young