Many scientists believe that Guinea baboons live in One Male Units (OMUs), which is a similar hierarchical structure to the hamadryas baboon. These OMU groups center around one adult male, and include adult females and juveniles of both sexes. The dominant male presides over a harem of females, and the OMU serves as both a reproductive group and a social group. OMUs occasionally mix together to create larger groups. This is called a fusion-fission society. Groups convene and break apart depending on the varying circumstances they face. When Guinea baboons feel threatened or vulnerable, they join together (fusion); foraging, on the other hand, is typically done in smaller groups (fission). There are also groups of AMUs (All Male Units), which are comprised entirely of male baboons. They are bachelors without harems.

One interesting observation that sets the Guinea baboon apart from other species of baboons is that males are seemingly okay with sharing females with males from other groups. The norm for baboons is a high level of competitiveness with regard to mating. Female Guinea baboons interact with males from other groups more than they do with females from other groups. Female Guinea baboons also have been known to interact with their female relatives who have moved on to be part of other OMUs.

It is important to note that a study in southeastern Senegal, which began in 2007 and was published in 2011, found that Guinea baboon social structure gives cause to reevaluate our overall understanding of baboon social structures. Typically, baboon social structures are seen as resembling one of two species: those of the hamadryas baboon, which is structured around small one male groups (OMUs) that fuse into a larger group; or those of the savanna baboon, which is centered around multi-male multi-female units (MMUs). Much of the literature available regarding Guinea baboons makes the assertion that they fall into the former category; however, over the course of the study, researchers found that the Guinea baboon social structure is actually quite fluid. The size and gender composition of groups changed often, splitting into smaller groups (fission) and convening into larger groups (fusion), as well as forming smaller all male groups (AMUs), smaller one male groups (OMUs), and larger multi-male multi-female units (MMUs). They also noticed seasonal variance in group sizes. For example, groups were larger during the rainy season than the dry season. Since the organizers of the study found that Guinea baboons didn’t seem to follow typical group patterns, they conclude that there needs to be more variance in the way in which we think about baboon social systems.