COMMUNAL NESTING IN PRAIRIE VOLES (MICROTUS-OCHROGASTER) - FORMATION,COMPOSITION, AND PERSISTENCE OF COMMUNAL GROUPS

We describe factors related to the formation, composition, and persist ence of communal groups in the prairie vole (Microtus ochrogaster). Co mmunal groups formed by the addition of philopatric offspring and unre lated adults to male-female pair and single-female breeding units. Alt hough unrelated adults did not join a group until at least two philopa tric offspring 30 days of age were present, there was no relationship between the presence of reproductively active philopatric offspring of the opposite sex and joining of unrelated adults. Most adults that jo ined a group were reproductive when they joined. Reproductive activati on of philopatric offspring was not related to the joining of unrelate d adults. During the breeding period all communal groups included 1 or more reproductive adults of each sex; in at least 75% of the groups, 2 or more adults of each sex were reproductive. There was no relations hip between low temperature, snow cover, or population density and for mation of communal groups. Dissolution of communal groups was not rela ted to reproductive activation of residents.