The differential responses to the odor of unfamiliar male conspecifics in dominant,subordinate, and isolated mice

Male ddY mice were used to investigate the responses toward the odor of unfamiliar male mice. They were reared either in isolation from 3 weeks of age or in pairs. At 10 weeks of age, they went through a 4-day test period, in which the responses of the mice toward the odor of unfamiliar dominant and subordinate mice were investigated by differentiating the responses into the time to investigate the odor and the final decision of avoidance or preference. All the mice went through the encounter tests after this odor test in order to investigate the relationship between the responses toward the odor and the behavior toward the odor donor. The pair-reared dominants and the subordinates responded to the odor of the dominant and subordinate mice differentially. This indicated that they could discriminate the dominance status of unfamiliar mice by odor. Isolated mice did not respond to the odor of the dominant and subordinate mice differentially. Social experiences were concluded to be necessary to discriminate the dominance status of unfamiliar mice through odor. The length of the investigation time and the final decision of avoidance or preference did not correlate in pair-reared or isolated mice, and these 2 scales were concluded to be different. But the dominant mice that investigated the odor for longer periods tended to show aggression in the later encounter test.