Endocrine induction of intermale aggression in mice: a comparison of hormonal regimens and their relationship to naturally occurring behavior

The level of intermale-like fighting behavior induced in female mice by various regimens of gonadal hormones known to establish aggression was compared. Regardless of whether the animals were exposed to testosterone propionate on the day of birth, the highest aggression scores were observed following chronic testosterone exposure in adult life. Females so treated also exhibited significantly more aggression than intact males. The least effective regimen was neonatal exposure to estradiol benzoate followed by long-term exposure of the adult to testosterone. Lastly, while castrated adult males were less likely to display aggressive behavior, those that fought did so at a level comparable to that of intact males.