Multiple human psychiatric disorders are associated with unusual social behaviors related to aggression, anxiety, and affiliation. Although the genetic component of these disorders is well established, their inheritance is complex and identification of the causative genes is often extremely difficult. The growth of phenotypic and genetic information, however, revealed that unusual behaviors observed in these disorders often represent the extreme ends of behavioral variation observed in the general population, suggesting that genes implicated in social behavior in unaffected population also influence disorder risk and symptom severity. To identify the genes and pathways disturbed in psychiatric disorders, an understanding of the molecular basis of mammalian social behavior would provide a crucial step forward. The goals of this project are to resolve differences in affiliation, aggression, and anxiety- like behaviors segregating in the red fox (Vulpes vulpes) with the intent of providing valuable insights into the mechanisms underlying a broad range of mammalian social behaviors, including human psychiatric disorders. The specific fox strains developed at the Institute of Cytology and Genetics (ICG) of the Russian Academy of Sciences exhibit markedly different, genetically determined behavioral phenotypes with significant parallels to typical and atypical human behaviors. The fox strains are well prepared for genetic, molecular, and cellular studies of social behavior and represent a unique, novel, and significant large animal model. The identification of molecular mechanisms influencing social behavior in foxes is expected to provide new insights into human disorders of social behavior and facilitate integration of human and rodent studies, thereby leading to the development of potential therapies.