Long-tailed macaques live in multi-male groups consisting of about thirty members. At sexual maturity, males leave their natal group, and join either bachelor groups or new social groups. Since males leave the natal group, they are subject to more predation, disease, and injury thna are females. Once a male finds another group in which to reside, he may replace some of the existing high-ranking males. Male replacement itself is a process in which a foreign male adult successfully takes over a resident male's harem position. These events are highly aggressive activites, and the participating adults are usually injured.
Despite aggression between males, this species is characterized by a genral lack of aggression between groups. Intergroup interactions are avoided/ When these groups meet, there tend to be high levels of aggression, involving chasing the non-resident group out of the area. Loud vocalizations and branch-bouncing are characteristic parts of these interactions. Males and females may use open mouth threats. This involves showing the enemy the incisors and canines, and pulling the ears and nose back. The alpha male is usually the one who leads the aggression by doing 90% of the branch-bouncing.
Within groups, a strict linear dominance hierarchy develops among males. This hierarchy is determined by such factors as age, size, and fighting skills.
Since females do not disperse, they are the stable core of a group. Females have a tendency to have close bonds with their maternal relatives throughout their lives. There is, however, a dominance hierarchy among females in a group. The acquisition of rank involves active intervention by maternal kin, and the differential treatment by unrelated members of the group. Grooming among females is a common activity. It is especially common for low-ranking females to groom higer-ranking females. This allows the lower-ranking females to receive less harassment, more support in aggresive interactions, and access to limited resources.
Long-tailed macaques are unique among other non-human primates because of their ability to show learned or cultural behavior. This cultural behavior was observed in the preparation of food by long-tailed macaques. On one occasion, an adult female dipped a piece of fruit into a river and then she consumed it. It was proposed that perhaps the female was cleaning sand off the fruit. Scientists investigated this further on other individuals who showed this behavior. Some of the macaques washed sandy fruit in the river, but some of them also washed fruit the scientists had cleaned prior to distributing them. There were also long-tailed macaques that simply ate the cleaned fruits without washing them. The controversy of what cultural behavior means is still being researched.
The day range of this species averages 1,900 square meters. The total of all the day ranges, or the home range, of this species averages 125 hectares.
The information on learned behaviour needs revision. Learned behaviour was first documented on chimpanzees, and has been found in other primate species. As well, I think the fruit-washing description above concerns Imo, a Japanese macaque who learned to wash her potatoes in the water, and later dropped rice in the water to separate from sand.