Mouse killing, insect predation, and conspecific attack by rats with differing prior aggressive experience.

Mouse-killing, cockroach predation, and conspecific attack were examined in male Long-Evans rats with a history of intraspecific aggression (n = 20), defeat (n = 20), or no aggressive experience (n = 20). Roaches were more likely to be attacked during 30 min tests, and were attacked more rapidly than mice or rats regardless of previous social experience of subjects. Rats with aggressive experience attacked conspecifics more readily than subjects with defeat or no experience.