RESPONSE OF YOUNG FEMALE PRAIRIE VOLES (MICROTUS-OCHROGASTER) TO NONRESIDENT MALES - IMPLICATIONS FOR POPULATION REGULATION

We measured behavioral and physiological responses to nonresident males of young female prairie voles (Microtus ochrogaster) living in family groups. Although substantial variation both among families and among littermates was noted, females generally exhibited investigative and affiliative behavior toward nonresident males, and many were reproductive at the end of a 10-day period. Approximately 31 and 56% of females exposed to sexually inexperienced and experienced males, respectively, had uterine weights greater than or equal to 30 mg. Females exposed in the absence of their fathers to sexually experienced males displayed the highest levels of interaction with nonresident males, and 71% were classified as reproductive. Control females, exposed either to castrated nonresident males or not exposed to nonresident males, remained nonreproductive. Frequent interactions with nonresident males can thus override the reproductive suppression experienced by young female prairie voles at natal nests. The resultant increase in proportion of reproductive females within each family group may contribute to dramatic increases in population density. By limiting interactions between their daughters and nonresident males, resident males play a role in population regulation.