EFFECT OF VOMERONASAL ORGAN REMOVAL ON BEHAVIORAL ESTRUS AND MATING LATENCY IN FEMALE MEADOW VOLES (MICROTUS-PENNSYLVANICUS)

The vomeronasal organ (VNO) mediates the induction of behavioral estru s in prairie voles by male chemosignals; however, the importance of th is system for the initiation of estrus in meadow voles, a species in w hich spontaneous estrus has been postulated, is unknown. This experime nt was designed to investigate the influence of VNO-mediated chemosens ory information on behavioral estrus in meadow voles housed in photope riods simulating summer (long photoperiods; 14L:10D) and winter (short photoperiods; 10L:14D). The VNO was removed from nulliparous female m eadow voles, and the percentage of animals mating after removal and th e timing of mating onset were assessed. Removal of the organ did not s uppress mating or change the timing of mating onset in females housed in short photoperiods. In animals housed in long photoperiods, in cont rast, removal of the organ significantly increased the percentage of f emales mating and the percentage of females mating rapidly after pairi ng. The results indicate that chemosensory information mediated via th e VNO is not necessary for the induction of behavioral estrus in meado w voles and lends support to the hypothesis that meadow voles have a s pontaneous estrus. We postulate that polygynous, solitary meadow voles reproduce more effectively with spontaneous estrus than with the indu ced estrus described for monogamous, group-living prairie voles.