Submissive behaviour is affected by territory structure in a social fish

Group living may engender conflict over food, reproduction, or other resources and individuals must be able to manage conflict for social groups to persist. Submission signals are an adaptation for establishing and maintaining social hierarchy position, allowing a subordinate individual to avoid protracted and costly aggressive interactions with dominant individuals. In the daffodil cichlid fish (Neolamprologus pulcher), subordinates may use submission signals to resolve conflicts with dominant individuals and maintain their social status within the group. The complexity of the physical environment may affect the value of submission signals compared to fleeing or avoidance, which may require certain physical features such as shelters to be effective. We investigated how the ecological context affected the expression of submission in subordinate daffodil cichlids by examining their behaviour under different arrangements of the physical environment within their territories. We altered the number of shelters provided to daffodil cichlid groups and compared the interactions between dominant and subordinate individuals under each shelter condition by scoring the social and cooperative behaviours of the group members. We found that behaviours of group members were modulated by the environment: subordinates displayed fewer submission and fleeing behaviours in more structurally complex environments and dominants were more aggressive to subordinates when more shelters were present. Our results help to elucidate the role of the physical environment in the modulation of social interactions in group-living animals and may have implications for the welfare of captively housed social cichlid groups.