Who’s the boss? Assessing convergent validity of dominance measures in male laboratory mice, Mus musculus

Authors: BARABAS, AMANDA - Purdue University; LUCAS, JEFFREY - Purdue University; ERASMUS, MARISA - Purdue University; Cheng, Heng-Wei; GASKILL, BRIANNA - Purdue University

Submitted to: Journal of Animal Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2021
Publication Date: 9/7/2021
Citation: Barabas, A.J., Lucas, J.R., Erasmus, M.A., Cheng, H., Gaskill, B.N. 2021. Who’s the boss? Assessing convergent validity of dominance measures in male laboratory mice, Mus musculus. Journal of Animal Behavior. 8. https://doi.org/10.3389/fvets.2021.695948.
DOI: https://doi.org/10.3389/fvets.2021.695948

Interpretive Summary: Aggression among group housed male mice is one of the most common reasons for premature euthanasia and reduces preclinical research data validity and reproducibility. Aggression within a group is typically displayed by the dominant mouse, targeting lower ranking subordinates, thus the strategies for preventing aggression may be more successful if applied specifically to the dominant mouse. To determine the dominance hierarchy, the convergent validity of three dominance measures (urinary protein darcin, tube test score, and preputial gland to body length ratio) were assessed with wound severity and rankings based on home cage behavior. Data from this study show that protein darcin and preputial ratio are representative of home cage aggression and provide further insight on individual behavior patterns in group housed male mice. The findings provide insights for scientists to develop management strategies to reduce aggressive injury in mice and to increase preclinical research data validity and reproducibility.

Technical Abstract: Aggression among group housed male mice continues to challenge laboratory animal researchers because mitigation strategies are generally applied at the cage level without a good understanding of how it affects the dominance hierarchy. Aggression within a group is typically displayed by the dominant mouse, targeting lower ranking subordinates, thus the strategies for preventing aggression may be more successful if applied specifically to the dominant mouse. Unfortunately, dominance rank is often not assessed because of time intensive observations or tests. Several dominance measures have been developed, but none directly compared to home cage behavior in standard housing. This study assessed the convergent validity of three dominance measures (urinary darcin, tube test score, preputial gland to body length ratio) with wound severity and rankings based on home cage behavior, using factor analysis. Discriminant validity with open field measures was assessed to determine if tube test scores are independent from anxiety. Cages were equally split between SJL and albino C57BL/6 strains and group sizes of 3 or 5 (N=24). During the first week, home cage behavior was observed, and the dominance measures were recorded over the second week. After controlling for strain and group size, darcin and preputial ratio had strong loadings on the same factor as home cage ranking and were significant predictors of home cage ranking showing strong convergent validity. Tube test scores were not significantly impacted by open field data, showing discriminant validity. Social network analysis was also done to reveal that despotic power structures were prevalent, aggressors were typically more active and rested away from cage mates, and the amount of social investigation and aggression performed by an individual were highly correlated. Data from this study show that darcin and preputial ratio are representative of home cage aggression and provide further insight on individual behavior patterns in group housed male mice.