Communal nesting in prairie voles (Microtus ochrogaster): an evaluation of costs and benefits based on patterns of dispersal and settlement

We evaluated costs and benefits of group nesting in prairie voles (Microtus ochrogaster) by examining dispersal from communal nests. Nests at which dispersal occurred did not differ in size from those at which no dispersal was recorded, and most animals did not exhibit declines in body mass prior to dispersal. Of those animals which left communal groups that contained at least one potential mate, half left groups at which level of competition for mates was judged to be low as opposed to medium or high. Our data do not support competition for food or mates as important costs of group nesting. One probable cost to individuals living in family groups is lack of mating opportunity; about one-third of all dispersers were from groups composed solely of family members. Several of our findings suggest that energy conservation is not the primary reason for communal nesting in prairie voles. Reductions in winter group size typically did not precipitate dispersal, and most dispersers that settled into a nest in winter joined groups which were smaller than the groups they had left. Dispersal did not increase during snow cover. Benefits of group nesting in natural populations of prairie voles remain to be identified.