The peak birth period of the Japanese Macaque is spring. Baby monkeys cannot walk by themselves just after their birth, they begin toddle at about 7days. After couple of month, they get together to play with another baby for all day long. They learn a lot through their play. After one year, they can handle most of things on their own.

But still there are not so many differences between boys and girls.

We can gradually see the differences between boys and girls from over one year. Boys play with boys including elder boys, they like violent games such as chasing, wrestling and climbing or jumping off trees. On the other hand girls play with girls including elder girls.
A few years later boys get masculine body and play more intensely. Girls are interested in their siblings and babies bared by other females, and do motherly care for babies like grooming and holding.

Males become sexually mature at around 5-6 years, females at around 4-5years. They copulate and give birth.

Though the timing of their leave vary, all of males leave their natal troop. Sometimes several males make a group but in most cases they roam alone. We call such monkeys ‘Hanare-zaru’. In autumn season they approach a troop to get chances of copulation. They are never in the way and never out of the way and watching for an opportunity to copulate.

Very young or aged males are treated tolerantly but monkeys in the prime of manhood are regarded as an enemy from a troop which they chase. Males in the troop act menacingly against such intruders. But some of females have copulation with Hanare-zaru.

Most of Hanare-zaru leave the troop after the period of copulation but some of them stay in the troop. Males basically cross between troops in his entire life.

Females remain in their natal troop. There are many females and children in a troop. Because males leave the troop, the number of females and children are much greater than males. Related individuals (mother and her baby, grand children, brothers and sisters) stay together most of the time.

They eat, sleep and relax together also they backup each other when they have a fight. They always cooperate with troop members.
A troop contains multiple matrilineal families.

Females give birth every other year, one baby in one time and deliver it from midnight to dawn. Pregnant period is about 180days. One female has 10 babies in her entire life. The average length of life is 25-30 years.