OPPOSITE STRAIN-DEPENDENT DIFFERENCES FOR INTERMALE AGGRESSIVE-BEHAVIOR ELICITED BY INDIVIDUAL HOUSING AND HOUSING WITH A FEMALE IN THE MOUSE

Male mice of the C57BL/6 strain show a significant increase in aggress ion toward a nonaggressive mate conspecific following 72 hr of individ ual housing. However, this increase was no longer evident following 2 weeks of individual housing. When housed with a female, C57BL/6 mice s how significantly more aggression than singly housed mice of the same strain after 72 hr as well as 2, 4, 8 weeks of differential housing. M ale C57BL/6 mice housed with a female also show significantly higher l evels of aggression than DBA/2 mice living in the same housing conditi on after 4 or 8 weeks of differential housing. Finally, male DBA/2 mic e individually housed for 8 weeks are significantly more aggressive th an mice of the same strain housed with a female for the same time. The se results indicate that the increase in aggressive behavior observed following isolation and cohabitation with a female in the mouse is not the same phenomenon. (C) 1994 Wiley-Liss, Inc.