Phenotypic variability between Social Dominance Ranks in laboratory mice

Area of Science:

• Animal behavior
• Laboratory animal science
• Biomedical research

Background:

• Laboratory mice are widely used in biomedical and behavioral research.
• The social context, specifically dominance relationships, is often overlooked in experimental design.
• Dominance hierarchies may introduce confounding variables in animal studies.

Purpose of the Study:

• To investigate the presence and stability of dominance hierarchies in grouped mice.
• To determine if dominance rank correlates with behavioral and physiological variations.
• To assess if individual variation is greater between cages than within cages.

Main Methods:

• Housing male and female C57BL/6ByJ mice in same-sex groups of 5.
• Observing dominance hierarchies over three weeks under standard laboratory conditions.
• Measuring behavioral and physiological phenotypes across different dominance ranks.

Main Results:

• Dominance ranks exhibited instability over time, with most stability observed between weeks 2 and 3.
• Phenotypic measures were highly variable, showing no consistent relationship with dominance rank.
• Limited evidence suggested an association between phenotype variation and cage assignment for either sex.

Conclusions:

• Dominance hierarchies in grouped mice are dynamic and not consistently stable.
• Dominance rank does not appear to be a reliable predictor of behavioral or physiological traits in this model.
• The study challenges the assumption that inter-cage variation in mice consistently exceeds intra-cage variation.