ATTRACTIVENESS OF MALE ODORS TO FEMALES VARIES DIRECTLY WITH PLASMA TESTOSTERONE CONCENTRATION IN MEADOW VOLES

We examined the hypothesis that differences in androgen concentrations may cause differences in the attractiveness of male odors to female meadow voles, Microtus pennsylvanicus. Males that were to be used as odor donors were castrated and implanted with Silastic capsules filled with no hormone or one of four different amounts of testosterone. Four different odors from males were assessed for each comparison; the odors were from the anogenital area, feces, urine, and posterolateral region. Treatment of scent donor males with the lowest dosage of testosterone was not sufficient to increase the attractiveness of their odors above that of males receiving no hormone. The three higher dosages increased attractiveness in a dose-dependent manner. The shape of the dose-response curve differed across scents: two scents reached maximum attractiveness in the middle of the dose range and remained there at higher doses, whereas the other two scents continued to increase in attractiveness as testosterone titers increased. The results suggest that scent glands produce graded signals that reflect circulating testosterone titers.