OLFACTORY SENSITIVITY TO THE PHEROMONE, ANDROSTENONE, IS SEXUALLY DIMORPHIC IN THE PIG

Sexually dimorphic pheromone pathways have been used successfully to s tudy insect olfactory coding. As one of the few mammalian species with an identified sex pheromone, the domestic pig (Sus scrofa) may be an ideal vertebrate species in which to examine sex differences in olfact ory processing of a specific stimulus. In this experiment, androstenon e and control odor detection thresholds were measured in adult male, f emale, and castrated mate pigs. In an operant task, pigs were tested w ith descending concentration series of both androstenone and geraniol. All groups were equally sensitive to geraniol, but there was a sex di fference in sensitivity to the odor of androstenone. Female pigs' dete ction threshold was a dilution fivefold lower than the threshold for i ntact mates. Castrated males did not differ significantly from either males or females. This is the first example of a sexual dimorphism in sensitivity to a mammalian pheromone.