Do wild rats attack intruders?
Wild rats attack introduced intruders. However, these attacks are not sustained and the intruder is rarely seriously injured because he runs away. Once he runs far enough away, pursuit stops, and he is ignored (Telle 1966). Aggression toward intruders therefore seems to function to exclude intruders from resources like food, shelter, and sexual access to females available to residents, and to chase away surplus animals into adjacent areas. In captivity, intruders cannot run away, so conflicts tend to escalate into serious and sometimes lethal fights (more on wild rat aggression). What do the intruders do? In general, intruders do not attack resident rats. They spend most of their time defending themselves by boxing, laying on the back, and fleeing. They spend very little time being aggressive toward residents (Blanchard et al. 1975, Christie and Barfield 1979, Takahashi and Blanchard 1982). Intact male intruders tend to show a little more aggression when they meet a castrated resident
