Sex differences in spontaneous locomotor activity and rotational behavior in meadow voles

Sex differences in rotational behavior have been most clearly established i n laboratory rats with females exhibiting a turning bias. Here, using an au tomated open-field apparatus, locomotor activity and spontaneous rotational behavior were examined in diurnally crepuscularly active reproductive male and female meadow voles (Microtus pennsylvanicus). Meadow voles, being ind uced ovulators, permitted analysis of females in constant behavioral estrou s. Males displayed significantly greater levels of activity and also signif icantly greater levels of clockwise but not counterclockwise rotational beh avior relative to the females. Rotational behavior was less strongly relate d to activity levels in female as compared to male voles. In addition, fema les displayed an overall turning bias. These results contrast with findings from laboratory rats in which females are reported to display greater leve ls of both locomotor activity and rotational behavior. They are, however, c onsistent with the rotational bias evident in female rats. The present find ings confirm the presence of sex differences in rotational behavior and ind icate that factors other than activity levels are involved in the generatio n and/or expression of these sex differences. Sex differences in anxiety an d routine-like behavior (i.e., asymmetry in movement) are discussed as poss ible factors contributing to these male-female differences in rotational be havior. (C) 1998 Elsevier Science Inc.