Group housing and social dominance hierarchy affect circadian activity patterns in mice

Abstract

In this study, we investigated the effect of social environment on circadian patterns in activity by group housing either six male or six female mice together in a cage, under regular light–dark cycles. Based on the interactions among the animals, the social dominance rank of individual mice was quantitatively established by calculating Elo ratings. Our results indicated that, during our experiment, the social dominance hierarchy was rapidly established, stable yet complex, often showing more than one dominant mouse and several subordinate mice. Moreover, we found that especially dominant male mice, but not female mice, displayed a significantly higher fraction of their activity during daytime. This resulted in reduced rhythm amplitude in dominant males. After division into separate cages, male mice showed an enhancement of their 24 h rhythm, due to lower daytime activity. Recordings of several physiological parameters showed no evidence for reduced health as a potential consequence of reduced rhythm amplitude. For female mice, transfer to individual housing did not affect their daily activity pattern. We conclude that 24 h rhythms under light–dark cycles are influenced by the social environment in males but not in females, and lead to a decrement in behavioural rhythm amplitude that is larger in dominant mice.

A paradigm shift in translational psychiatry through rodent neuroethology

“…HCM can potentially minimize the 'experimenter effect'-the compromised standardization and reproducibility in behavioral tests caused by the gender of the experimenter or by differences in handling styles [65]. Prolonged monitoring of behavior in the home cage also increases statistical power and enables the analysis of the temporal dynamics of behavior [66,67]. However, individual caging of mice and rats affects their mental state and behavior.…”

Long-lasting effects of disturbing the circadian rhythm or sleep in adolescence

“…Specifically, there is research showing that social hierarchy may play an important role in determining circadian rhythmicity within a cage. Within group-housed cages, dominant male mice showed a larger percentage of daytime activity compared to their subordinate conspecifics, but this finding was not seen in females ( Robbers et al, 2021 ). This finding paves the way for further research into individual differentiation in chronotypes amongst mice, and the impact of social demands on circadian rhythmicity within mice.…”

Excess neonatal testosterone causes male-specific social and fear memory deficits in wild-type mice

“…Relatedly, we treated the entire litter with veh or testosterone and same-treatment mice remained housed together, but it will be valuable to address whether behavioral effects would be affected if litters consisted of mixed-treatment mice and to explore litter effects more carefully. Additionally, we did not account for social dominance or hierarchical status, which can affect behavior, although stability of social ranking and under which specific circumstances it affects behavior are complex (60)(61)(62)(63)(64). This will be interesting to investigate in future experiments.…”