Living in some kind of social grouping is not extraordinary among mammals, and it is certainly not unusual among primates. However, a majority of mammals does not live in large social units; many are solitary or live as mated adults with offspring. Of course, even solitary mammals have to engage in some social activities for mating, and the mother usually spends time feeding and protecting her infants. However, primates, including humans, do tend to form social groups. Normally, primate social behaviour and social group is based on ‘home range’ or the area frequently used by the animals. This area may be shared with other individuals of the same, as well as of other species. Belonging to the ‘fission-fusion’ society is the chimpanzee.

The chimpanzee is the smallest in its own group, which is The Great Ape. Its two species includes the common chimpanzee, which has a wide distribution from Guinea and Sierra Leone to western Uganda and Tanzania, north of the Zaire (Congo) River. Another is the bonobo or the pygmy chimpanzee, which lives in primary rainforests in one area of Zaire, south of Zaire River.

Chimpanzees live in loose communities of 9 to 120 animals. Common chimps live in loose extended troops that can include more than 100 individuals; bonobos live in much smaller troops, which often consists of less than 20 individuals. The social life of chimpanzees is more complex than that of other apes. They form several groups varying in size and composition, which is typical of a fission-fusion society. In such social organization, large troops break into smaller ones, which in turn combine with larger ones. That is why their members change repeatedly.

The females raise their young by themselves. The infants ride under the mother's body, supported by her arm, until they are about 5 months old. They then ride on the mothers’ backs. Chimpanzees leave their mothers at about 6 years of age. On the other hand, adult chimpanzees spend about an hour everyday in a social activity called ‘grooming’. During this period, two or more of them sit and pick each other's hair. They remove any dirt or insects that they may find. Chimpanzees occasionally engaged in fights, usually to establish their rank within the social group. They are also aggressive towards chimpanzees from other territories and tends kill them. Although they mainly feed on leaves, fruits, seeds and stem, chimpanzees occasionally kill and eat other mammals like the baboons and bush pigs. Because of the isolation of the region in which it lives, little is known about the ecology and behaviour of the bonobos.

Another Old World monkey family, besides the chimpanzee, is the colobus. There are six species; four of which come under black and white colobus while the others are red colobus. The black and white colobus are fairly large monkeys with noticeably long tails. The guereza or the black and white colobus spread across equatorial Africa from northern Tanzania to Abyssinian Highlands, in forest habitats. Angolan black and white colobus also ranges into East Africa.

Like for the chimpanzees, social grooming is very important in colobus social relations. Despite lack of proper thumb, grooming is often performed at higher rate than in most monkeys. Troops members demand to be groomed and occasionally, to groom. A colobus monkey stretches out in front of intended groomer to solicit grooming. If ignored, solicitor may slap the other’s cheek lightly to get its attention, then try again. Groomer sometimes comes up behind intended groomee and starts in. Other times, the groomer makes frontal approach and tugs the other’s head down to the desired position. If the groomee resists, the groomer smacks lightly on the head, followed by another forceful pull.

Guereza troops are unusually cohesive. Even while feeding, members sit close together as they pluck leaves. Females and young stay closest together, while subadult males stay furthest from the others. The oldest female mostly leads troop movements. However, a subadult male sometimes initiates hostile encounters with neighbours.

Like the black and white colobus, night monkey (also known as douroucouli) feeds on leaves and fruits. However, vertebrates and eggs are consumed occasionally and the male species actively participate in raising their young. The infant is only returned to the female when it needs to be nursed or fed. This happens mostly during the second and week of the baby’s birth. The siblings do not have any chance of carrying it. However, during the second half of the year, the young reaches the phase of complete independence where it starts playing with siblings. It then starts to relate more to the mother than the father, just like it used to in the first few moments of its birth. As you can see, might monkeys live in small groups, each consisting of a father, mother and the young. Hence, it is impossible to group more than one male and one female together without quarrels or fights occurring. Despite living in small, strictly monogamous groups, they feed in large, clumped food trees. They travel soundlessly and are relatively inactive. They may spend quite some time in a single fruit tree, moving around from time to time or sitting quietly. Chiefly nocturnal, night monkeys use elaborate visual, vocal, and sense of smell to communicate with each other. Besides, scientific studies have proven that these monkeys are most active in moonlight. In total darkness, they tend to push their activity later, during the earlier hours of daylight. Thus, like all other nocturnal animals, night monkeys sleep in bright phase and search for food during the dark phase.

In contrast to gibbons, night monkeys do not sing in duets, and calling sessions are restricted to once or twice a month. These calls are made at the beginning of their daily night activity. Often, the entire group joins in the so-called loud choral singing. Besides, they rarely fight during hoot nights. Nevertheless, when a neighbouring family group trespassed into a ripe fruit tree near a border, males and females of each group burst into a low, ascending resonating cries and attack. There are a couple of differences between troops of monkeys from different locations. For example, night monkeys from Bolivia are far livelier as compared to those from Colombia.
This is especially true in the first hours of their period of activity. They maintain more social contacts and does grooming more frequently. Even in parasite susceptibility, there is a contrast between the two groups of night monkeys; Colombia monkeys contract malaria, whereas the Bolivian ones do not.

Another best-studied primate is the savanna baboon. This is probably due to the open grassland in which they live, which enables humans to study them without much obstruction. Savanna baboon can be divided into 4 types, namely the olive, yellow, chacma, and Guinea baboons. Social organization in this primate is quite adaptable to fit various conditions. In addition, it varies from one troop to another. For example, the baboon troops at Amboseli, Kenya show intergroup aggression when they are very close together. On the other hand, baboons in Uganda move frequently from one group to another. Unlike both groups of baboons, the ones in Nairobi Park, Kenya, do not make much movement and remain in its group most of the time. The size of these troops ranges very widely; from as small as eight members, to as large as 200 members. In most cases, troops avoid each other unless to fight for scarce resources. In such situations, the larger troop will always succeed.

A baboon troop is one of the most complex societies among all animals. Social relations are based on gender, by male-female and male-male alliances, even emigration and immigration. This is probably brought about by the determination of these animals to attain and maintain their control. Their readiness to work together as a force is the reason why baboons can wander the savanna with impurity, even in the presence of predators. They defend their territories to preserve resources and protect themselves from enemies and predators. The social behaviour, however, is not biologically determined. It depends on the size of the home range and troop size. For example in places where there are no territories, the home ranges of baboon troops overlap extensively. Unlike the gibbon, the baboon troops tend to ignore one another when more then one troop occupies the overlapping area. There was not much contact either. Either they totally ignore one another, or the smaller troops simply gives way to the larger ones. However, core areas (part of a home range containing concentration of food, a water hole and other resources) are utilised by a single troop. This troop will spend almost the whole day in this area.

Although food can be easily found, the baboons have to find most of its food on the ground. Accordingly, danger from predators poses a real threat and thus, the place they sleep has to be ensured safe. This has to be done by nightfall. The troop is highly dependent on the male during daytime, basically for protection. These male baboons will warn the whole troop if they spot any predators and when danger is alerted, the whole troop races for protection. However, the males and some adult females will stay behind as rear guards.

The adult male baboons are arranged in a dominance hierarchy. Most dominant male baboons are physically strong and appear to be confident, aggressive and able to get support from other males. These groups of baboons are often seemed to be the offspring of highest-ranking female. The presence of these females enables the baboon to intimidate other animals, especially those of higher than his rank, but lower than the mother’s. The mother, on the other hand, will back up the young in a conflict situation. As members grow old and die, changes are made to the hierarchy but young males cannot simply challenge the most dominant male for his position. This is because the most dominant male is more likely to have the support of the other males. However, it is possible for some high-ranking males to maintain their high rank even after they are old and weak. As for the females, the rank is usually determined by the rank of the mother, the female young will always be ranked just below her mother. But unlike the females, subadult baboons leave the troop and migrate to other troops. Such migrations cover long distances and expose these male baboons to a lot of danger. This is why males have a higher death rate and do not form close bonds with family members, as the females do.

Female baboons are usually wary around large adult males. Ironically, female form friendship with certain males. The relationship is quite different in the sense that the adult female is more relaxed around her male friend and often grooms him. The male friend, in return, offers protection to both the female and her infant. These baby baboons are usually given birth at night. This could be the reason why the births are rarely witnessed. Nonetheless, the baby is normally carried by its mother using one arm. Therefore, the mother has difficulty catching up with the troop. After 3 to 4 months, the baby begins to play in the subgroup formed by females with small young. However, they still depend on their mother for food and transport. This continues for about another half year.