Social organization and mating system of free-living prairie voles Microtus ochrogaster
We summarize the social organization and mating system of the prairie vole, Microtus ochrogaster, as determined from an extensive field study in east-central Illinois, USA. The fundamental social organization of M. ochrogaster consists of communal groups formed from an original male-female pair or single female (usually a survivor of a male-female pair) by addition of philopatric offspring and unrelated adults. Philopatric offspring comprise 70% of additions to the original breeding unit. In addition, most (80%) unrelated adults do not join a family group until at least two philopatric offspring have reached adult age. Thus, formation of communal groups is based on a high level of philopatry. Male-female pairs display traits associated with behavioral monogamy, including sharing a nest and home range, mate-guarding by the male, and paternal behavior (grooming, huddling, and retrieval of young). Members of communal groups also defend the group territory [Acta Zoologica Sinica 51(2): 178–186, 2005].