Sex differences in agonistic social behavior: Effects of exercise and ovariectomy

Aggressive behavior encompasses a range of offensive and defensive responses that may be differentially influenced by sex, ovarian hormones, and physical activity. However, much of the existing research has focused on males and utilized paradigms designed to elicit aggression, leaving the expression and regulation of offensive and defensive behaviors during other forms of social interaction poorly understood. Here, we investigated the effects of sex, voluntary wheel running (VWR), and ovariectomy (OVX) on agonistic behavior during juvenile social exploration in adult Sprague-Dawley rats. Males exhibited greater offensive aggression, characterized by increased aggressive grooming and pinning, whereas females displayed more defensive kicking, darting, and avoidance. OVX selectively reduced defensive kicking without significantly affecting offensive aggression or avoidance, suggesting that distinct behavioral responses differ in their sensitivity to ovarian hormone removal. In contrast, VWR did not significantly alter any of the behaviors examined. Importantly, exploratory composite analyses revealed a significant sex difference in offensive aggression that was no longer detected when defensive behaviors were incorporated into the measure. Together, these findings demonstrate that sex differences in agonistic behavior extend beyond overall levels of aggression to distinct patterns of offensive and defensive responses. Distinguishing these behavioral categories may therefore be important for identifying how various manipulations, such as sex, ovarian hormones, and physical activity, influence agonistic behavior.