Dominance and aggression in social groups of male and female rats.

Two experiments were performed to examine aggression and dominance in domestic male and female Rattus norvegicus living in small mixed-sex (3 males and 3 females) groups. Experiment 1 examined the development of aggression in females. A single female (alpha) within each of the six colonies tested showed the preponderance of attacks on male intruders placed into the home-cage when male colony residents were absent.