CHEMICAL CUES ARE NECESSARY BUT INSUFFICIENT FOR REPRODUCTIVE ACTIVATION OF FEMALE PINE VOLES (MICROTUS-PINETORUM)

Among various arvicoline rodents, reproduction is influenced to varyin g degrees by social factors, including behavioral or chemical cues, Si nce previous research suggested that chemosignals from adult males rep roductively activate female pine voles (Microtus pinetorum), we sought to determine specifically what types of stimuli promote the activatio n response. In these experiments, females were exposed to unfamiliar a dult males, or to some combination of cues from males, or were housed alone. Using uterine mass as a measure of reproductive activation, we found that females were not activated by exposure either to male urine by itself or to male-soiled bedding by itself, but full contact with a male clearly resulted in heavier uteri. Females whose vomeronasal or gans were surgically excised failed to undergo reproductive activation when housed with males. Finally, females allowed physical contact by being housed directly underneath males had heavier uteri than did fema les whose housing allowed contact only with the chemical cues from mal es. Among female arvicoline rodents, it appears that there exists a ph ysiological continuum between absolute dependence on both contact and chemical cues from males vs. absolute independence for reproductive ac tivation, The present results place female pine voles closer to the fo rmer extreme than to the latter.