Two important factors that influence social structure of this species are: seasonality and kinship.
Seasonality
During the dry season, core groups are much smaller, and small sub-units often do not fuse with larger groups. Conversely, during the wet season, smaller groups are more likely to fuse with other small groups to create a large social group. This can be explained simply by the availability of resources. Resources are scarce during dry seasons, thus groups can reduce resource competition by staying in smaller groups. But, there is an abundance of resources available during wet season, and individuals are more likely to benefit from the protection provided by staying in larger groups.
Kinship
Kinship also has an equally important role in determining the social structure of an African elephant social group. The core group is often composed of female elephants and their close relatives (Vance, Archie & Moss 2009). Related females tend to form core social groups against unrelated females, and older, experienced matriarchs consistently dominate smaller, younger matriarchs (Archie et al. 2006).
Male sociality
Unlike the female elephants, male elephants spend most of their lives alone, in a mixed group of males and females, or in an all male group. Like many male mammals, strong social bonds are not very widespread in African elephant societies. Male association within an all male group is correlated with genetic relatedness and age. Adolescent males (10-20 years of age) are the most sociable age group, and prefer stay in close proximity to other elephants. Young males choose to associate with other males closer to their age, perhaps to use as sparring partners to practice for future male-male competition (Chiyo et al. 2011). As males get older, they tend to spend more time alone, or around males older than 35 years of age (Evans & Harris 2008). It has been hypothesized that males prefer to have older males as neighbors to learn from more experienced elephants.