Female meadow voles (Microtus pennsylvanicus) demonstrate same-sex partner preferences.

Female meadow voles (Microtus pennsylvanicus) are territorial during warm months but demonstrate social tolerance under low temperatures. In spring, females nest together and some pairs participate in communal nursing and rearing of young. Because communal nursing involves significant cooperation, selective pair-bonds may develop between 2 nestmates. Using a choice apparatus, the authors determined that (a) captive females demonstrated partner preferences for a nestmate; (b) partner preferences were enduring and persisted after dyadic separation; and (c) following the loss of a nestmate, females did not develop preferences for a new nestmate, even after extended cohabitation. Data support the hypothesis that captive meadow voles develop selective and enduring same-sex social bonds that may, under free-living conditions, facilitate communal nesting and cooperative rearing of young.