Group Social Dynamics in a Seminatural Setup Reflect the Adaptive Value of Aggression in Male Mice

Background

Maladaptive aggression in humans is associated with several psychiatric conditions and lacks effective treatment. Nevertheless, tightly regulated aggression is essential for survival throughout the animal kingdom. Studying how social dominance hierarchies regulate aggression and access to resources in an enriched environment (EE) can narrow the translational gap between aggression in animal models and normal and pathological human behavior.

Methods

The social box is a seminatural setup for automatic and prolonged monitoring of mouse group dynamics. We utilized the social box to decipher tradeoffs between aggression, social avoidance, resource allocation, and dominance in 2 mouse models of increased aggression: 1) a model of early exposure to an EE and 2) a model of oxytocin receptor deficiency (Oxtr^−/−). While environmental enrichment increases aggression as an adaptive response to external stimuli, hyperaggression 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 groups 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.

Conclusions

Measuring aggression and social dominance hierarchies in a seminatural setup reveals the adaptive value of aggression in EE and Oxtr^−/− mice. This approach can enhance translational research on pathological aggression.