Detailed characterization and analysis of intraspecific aggressive and defensive behaviors of rats in mixed sex groups is beginning to provide an understanding of the complex pattern of behavioral and physiological change associated with variation in dominance status. These findings indicate that male subordination dramatically reduces longevity and produces a pattern of behavior changes very similar to the defenses elicited by predatory exposure. In addition, many of these changes are, in detail, isomorphic to important behavioral features of clinical depression.