[Competition for limited environmental resources on the social dominance model in laboratory mice]

Asymmetry of social rank in the competition for food and female was studied using the social dominance model with only two male mice. Marking activity was recorded as a useful indicator of the social status. Social rank was determined by asymmetry in aggressive behavior. A food test was presented for 10 min daily within 5 days of the experiment, whereas a sexual test was performed only on the 5th day for 30 min. Marking behavior was estimated twice: before the first interaction and on the 4th day of the experiment. The competition for food was accompanied by active attacks, escapes, vertical defense postures, and sniffing. The level of aggression, sniffing, and food activity was higher in dominant than submissive males. Time course of aggressive, defensive, and sniffing behaviors was characterized by maximum scores in the period of formation of social hierarchy; however, the rate of food activity in this period was low and increased only to the 4th day. Introduction of a receptive female into the male group with the stable social hierarchy stimulated the intermale aggression, defensive and sniffing behaviors. Dominant males were characterized by a greater number of victories over and sniffing contacts with both male and female. Marking activity was also more intense in dominants. Thus, significant unidirectional rank differences in agonistic, sniffing, food, sexual, and marking behaviors were shown on the social dominance model with the minimum number of partners.