Social Organization of the Prairie Vole (Microtus ochrogaster)

Abstract

In microtine rodents, formation of communal groups often is associated with environmental stresses of winter or high population density. Social organization of the prairie vole ( Microtus ochrogaster ) consisted of communal groups formed by addition of philopatric young and unrelated adults to an original male-female pair or single-female breeding unit. Owing to high juvenile mortality during spring-early autumn, most social groups remained as male-female pairs or single females. Male-female pairs displayed behavioral traits associated with monogamy, including sharing a common nest and home range, mate guarding, dissolution of pairs by mortality, and low incidence of remating. Male-female pairs rarely involved related animals. Single-female breeding units were survivors of male-female pairs that had not formed a new pair; prevalence of single-female breeding units was not related to availability of unpaired males. When juvenile survival increased in late autumn, communal groups became the predominant social group. Formation of communal groups was unrelated to low temperatures and was not contingent upon the nonreproductive status of members. Although present at low population density, communal groups were the most common type of social group at high densities. We conclude that increased survival of juveniles in late autumn leads to the formation of communal groups and increases in population density.