The effects of cross-fostering on the development of social preferences in meadow voles (Microtus pennsylvanicus).

To determine the role of the parental environment in the formation of species attachments in the meadow vole (Microtus pennsylvanicus), young of this species were fostered to either meadow vole parents (in-fostered young) or to prairie vole parents (M. ochrogaster; cross-fostered young). At 50 to 60 days of age, subjects were tested for social preference in an environment that simulated the conditions of a runway system. The testing design assessed the reaction of fostered animals to a novel species (M. pinetorum) as well as to the parental and biological species. The proportion of total test time spent near stimulus animals did not vary as a function of rearing condition. However, when compared to in-fostered controls, cross-fostered meadow voles displayed increased preference for prairie voles. Novelty did not appear to be a significant factor in test animal choice. These results suggest that in meadow voles, preference for the species of social partner is dependent on postnatal experience with parents.