York, C. A., Schulte, B. A. 2014. The relationship of dominance, reproductive state and stress in female horses (Equus caballus). Behavioral Processes 107, 15-21.
Maintaining a dominant position in a hierarchy requires energetically expensive aggressive displays and physical exertion. Lab based winner–loser studies, often conducted with individuals from non-social species, have shown that subordinates have higher stress hormone levels...