Chimpanzees (Pan troglodytes) are highly social animals whose societies can be described by perpetual associations and great levels of cooperation among individuals. However, the fact that the individuals compete for resources such as food and water can lead to aggression among them. Reasons which can lead to such aggressive interactions in chimpanzees are personal defense, protection of certain conspecifics and competition. Another reason that can lead to aggression in captive chimpanzees is limited space. The spatial crowding hypothesis suggests that chimpanzees under crowded conditions are subject to increased conflicts of interest.

Furthermore, captive chimpanzees need a high amount of social and environmental complexity to bring their behavioural repertoire and activity status as close as possible to that of their wild conspecifics. Without such social and environmental complexity, they might display health and behavioural problems. Thus, the use of environmental enrichment (any actions taken to improve the physical and psychological wellbeing of captive animals) in captive environments is essential.

Aim of this study was to investigate and compare the social interactions in a group of twenty captive chimpanzees between two different periods: outdoors (summer) and indoors (autumn) and to identify if the presence and the type of enrichment affected the social interactions in the group.