Group social dynamics in a semi-natural setup reveal an adaptive value for aggression in male mice

Background Maladaptive aggression in humans is associated with several psychiatric conditions and lacks effective treatment. Nevertheless, aggression constitutes an essential behavior throughout the animal kingdom as long as it is tightly regulated. Studying how social dominance hierarchies (SDH) regulate aggression and access to resources in an enriched environment (EE) can narrow the translational gap between aggression in animal models and humans normal and pathological behavior. Methods The ‘social box’ (SB) is a semi-natural setup for automatic and prolonged monitoring of mouse group dynamics. We utilized the SB to decipher complex tradeoffs between aggression, social avoidance, resource allocation, and dominance in two mouse models of increased aggression: (i) a model of early exposure to EE and (ii) a model of oxytocin receptor deficiency (OxtR -/- ). While EE increases aggression as an adaptive response to external stimuli, hyper-aggression in OxtR -/- mice is accompanied by marked abnormalities in social behavior. Results EE groups exhibited significant social avoidance, and an increased proportion of their encounters developed into aggressive interactions, resulting in lower levels of exploratory activity and overall aggression. The hierarchy in EE was more stable than in control groups, and dominance was correlated with access to resources. In OxtR -/- groups, mice engaged in excessive social encounters and aggressive chasing, accompanied by increased overall activity. In OxtR -/- groups, dominance hierarchies existed but were not correlated with access to resources. Conclusion Measuring aggression and social dominance hierarchies in a semi-natural setup reveals the adaptive value of aggression in EE and OxtR -/- mice, respectively. This approach can enhance translational research of pathological aggression.