**2.1. OXT and male animal affiliation**

While most studies of both AVP and OXT conclude that OXT is a more important mediator of affiliative behavior in females than males, there is considerable evidence that OXT may serve important social behavior functions in males as well. The most convincing evidence for the role of OXT in affiliative behavior in animals is pair bonding in prairie voles (*Microtus ochrogaster*). These voles are relatively unique in their monogamous social structure, which is mediated by OXT and AVP activity in the brain. Central OXT infusions facilitate prairie vole pair bonding [3], which has been linked to gender specific developmental effects in male voles [4]. The distribution of OXT receptors in the brain mediates divergent social strategies in monogamous and polygamous vole species [5]. Studies of social recognition and memory in male mice, processes important for the establishment of affiliative behavior, conclude that OXT actions on social behavior are mediated by changes in recognition and social memory [6, 7]. In male rats, OXT facilitates sexual behavior through actions in the PVN [8]. In pair bonded tamarin monkeys, peripheral OXT levels vary with levels of affiliation and sexual behavior in both genders [9]. Specifically, OXT levels in male tamarins were correlated strongly with sexual behavior. In fish it has been postulated that isotocin (the teleostean homologue of OXT) is involved in courtship displays and territorial defense [10], and many of the social behavior effects of OXT are conserved across taxa [11].
