Work has shown that the ventrolateral division of the ventromedial hypothalamus (VMHvl) encodes a generalized state of social threat and is necessary and sufficient for producing both social aggression and avoidance. However, it remains unclear how the selection between aggression and avoidance occurs and how this selection might support the animal's adaptation to its environment.We have shown that neurons in VMHvl that fire in the context of social defeat are reactivated when the animal explores the location where the defeat occurred, even in absence of the aggressor. At the neural population level, following social defeat VMHvl firing becomes tuned to the context where the animal is located, discriminating between the home cage and the chamber where the aggression took place. We hypothesize that the VMH may encode a functional map of territorial space that guides context-appropriate social threat responses. To test this hypothesis, we developed an experimental apparatus that allows for the study of territorial behavior under semi-natural conditions. Pairs of male mice in the apparatus exhibited a stereotyped evolution of dominance hierarchies and the context-specific expression of social aggression and avoidance. Moreover, we found that, unlike outbred mice, laboratory inbred mice were unable to express stable territorial behaviors in the apparatus. Finally, we developed a novel dual-color fluorescence detection method to track urine marking patterns in freely interacting mice. We are using this apparatus to test several hypotheses about the neural control and encoding of territorial behaviors in mice.