It’s definitely not the men’s prisons. This study says the two are equal:
This study estimates prevalence rates of inmate-on-inmate and staff-on-inmate physical victimization. Inmate participants were drawn from 13 adult male prisons and 1 female prison operated by a single mid-Atlantic state. A total of 7,221 men and 564 women participated. Rates of physical victimization varied significantly by gender, perpetrator, question wording, and facility. Prevalence rates of inmate-on-inmate physical violence in the previous 6 months were equal for males and females. Men had significantly higher rates of physical violence perpetrated by staff than by other inmates. By facility, inmate-on-inmate prevalence rates ranged from 129 to 346 per 1,000, whereas the range for staff-on-inmate was 83 to 321 per 1,000 (but the difference was not statistically significant).
Source: “Physical Violence Inside Prisons, Rates of Victimization” from Criminal Justice and Behavior
And in his excellent book “Codes of the Underworld: How Criminals Communicate” Diego Gambetta explains:
Women are significantly less violent than men in the outside world and less lethal when they are violent. This holds in all time and places for which relevant data exist. And yet in prison this universal fact is overturned: women become at least as violent and often more prone to violence than men are. Although women in prison rarely commit homicide, a large study of Texas prisons by Tischler and Marquart showed that there was no difference between women and men in violent episodes. Table 4.2, based on comprehensive statistics for England and Wales, shows that the gender pattern is even reversed: women assault each other twice as much as men do, and they fight one and half times as much as men do…