Mate choice is based on the assessment of attractiveness of traits possessed by potential mates. These cues can be chemical, visual or auditory and choice is often based on perceived direct or indirect benefits to fitness that can be conferred by choosing a given partner. The degree of “choosiness” an individual can exercise is determined by the availability of potential mates and the likelihood of meeting them. These factors are influenced by territorial boundaries and the personalities of those who enforce them. In order to investigate the role of these two factors in mate choice and fitness, we tested two recently diverged (3000 years) populations of house mice, which were found to follow a specific mating pattern in previous semi-natural enclosure studies (Montero et al. 2013). Experiments under controlled cage conditions and in semi- natural environments were applied to define behavioristic traits of the two mouse populations mentioned above. In the latter environment small populations of mice were kept in three replicate rooms. Mouse movement, group formation and interactions are recorded over six months by RFID antennae technique; mating success will be established by microsatellite genotyping. Territoriality, migration and several personality traits including risk-taking, activity, novelty-seeking and aggression will be assessed regularly. Evidence exists for different territorial abilities and different migration patterns between the two mouse populations, as well as sex specific differences in territory use. To what extent behavior in general and personality specifically influence an individual’s fitness will be determined after successful paternity analysis for all offspring born in the enclosures.