Food competition, but not other common assays, reveals social dominance in female and male CD1 mice.

Social dominance is fundamental to social organization across species and plays a critical role in shaping behavior, physiology, and health. Despite the complexity of social organization, researchers have successfully developed animal models to investigate social dominance under controlled experimental conditions across a variety of species, including male rodents. However, measures of social rank among female mice remain poorly understood, limiting the generalizability of commonly used social dominance assays. Here, we systematically evaluated four commonly used behavioral assays of social dominance in female CD1 mice and directly compared their performance with that observed in males. We found that three traditional assays-agonistic behavior, urine marking, and the tube test-failed to distinguish social rank in female CD1 mice. In contrast, the food competition task reliably identified social ranks in both female and male CD1 mice, revealing linear dominance hierarchies and demonstrating that this assay effectively assesses social dominance across sexes in an outbred mouse strain. By systematically comparing multiple behavioral assays in female and male CD1 mice, our study expands the current understanding of how social dominance is expressed across sexes and establishes a valuable platform for future studies aimed at uncovering the neural mechanisms underlying social hierarchy.