Effects of Social Stimuli on Testosterone, Aggression, and Fighting Behavior in Male Golden Hamsters (Mesocricetus auratus)

Abstract

Testosterone has long been implicated in aggression. However, evidence for its role is contentious. This study examined the influence of testosterone on aggression but also aimed to further explore the effect of previous social stimuli on the outcome of male-male fights. Experimental males were exposed to animal stimuli (males, diestrus females, or estrous females) through a mesh barrier, and then testosterone levels were measured. The following day, control males with no prior exposure fought experimental males, and fighting behavior was recorded. It was hypothesized that exposure to social stimuli, especially exposure to estrous females, would induce testosterone surges in males. These surges would increase aggression in fights, thereby improving fighting ability in males with prior exposure. It was predicted that higher aggression would translate into experimental males winning significantly more fights than their control counterparts. However, results were rather ambiguous. A significant testosterone surge in males was only found after exposure to diestrus females. Males exposed to estrous females exhibited nearly significant testosterone surges, whereas males exposed to other males showed no significant changes in testosterone. The significant testosterone rise in males exposed to diestrus females did seem to increase aggression during fights compared to males with only male exposure. However, this did not predict the outcomes of the fights as expected.