Warm Spot Test as a Correlate of Social Dominance in Mice: Evaluating Animal Behavior Tracking Methods

Abstract

Dominance hierarchies occur naturally in both primate and non-primate species when resources are limited. They allow for organization between groups or populations in order to minimize conflict, allocate available resources, and ensure survival. Mice are commonly used as a model for social dominance as their behavior can be quantified through assay-specific metrics or by tracking their position and movement. The tube test is the gold standard for measuring social dominance through numbers of wins, but several other assays are used as correlates of social dominance, often to validate tube test results. These include the warm spot test and the wet bedding avoidance (WBA) test. This study employs C57BL/6 caged, male mice in a tube test and the warm spot test (WST) paradigm. The cumulative amount of time each mouse spends in the warm spot is manually recorded from 20-minute trials. Using Spearman’s rank correlation, warm spot test results show a relatively weak correlation with tube test results: Warm spot test may be a potential predictor of social dominance in mice, but the evidence does not provide strong support. This study asks whether there are better methods of assessing the validity of the warm spot test than manual tracking. We employ SLEAP (Social LEAP Estimates Animal Poses), a program utilizing deep learning software to track animal position changes and predict behavior. SLEAP can train models from labeled parts of mice and uses multi-animal tracking with high accuracy. After quantifying a hierarchy from SLEAP data from a single cage of mice that underwent the WST, we perform correlational analysis with tube test data. The hierarchy derived from SLEAP matched that of the tube test (Spearman ρ = 1.00), whereas the hierarchy from manually tracking warm spot occupancy swapped the top two-ranked mice (Spearman ρ = 0.80). Despite only being performed on a single cage, we still gain an understanding of the efficacy with which SLEAP data can validate the warm spot test to serve as a correlate of social dominance. The ability for SLEAP and deep-learning methods in general to track animal behavior in an unbiased and systematic manner can fill methodological gaps and may be a vital tool in ethological studies.