Kinship, familiarity, aggression, and dominance in deer mice (Peromyscus maniculatus) in seminatural enclosures.

This study was designed to test the effects of kinship and postweaning familiarity on male-male aggressive interactions in deer mice (Peromyscus maniculatus) in a more naturalistic situation than that of most tests of kin discrimination. Familiar males (i.e., those housed together from weaning) displayed significantly less aggression than unfamiliar males; kinship per se did not appear to affect levels of aggression. In addition, dominant males copulated more than subordinates and under some conditions sired more offspring. The postest copulatory patterns showed that the subordinate males ejaculated after fewer intromissions than did dominant males.