Sex pheromones and aggressive behavior in male rats

Two experiments were performed to examine the relationships among the sexual cycle of the female, sex pheromones, and the agonistic behavior of male rats. Data suggest that the presence of an inaccessible sexually receptive female provokes increased intermale fighting. The present research investigated the possibility that a sex pheromone from the female mediates the change in male hostilities. In Experiment 1, a combination between-subject and within-subject design was used to expose half the males to the female by several sensory modalities. The other males were exposed to the female primarily by olfaction. In Experiment 2, a completely between-subject design was used to expose some males only to the soiled bedding of the female. The results suggest that olfaction is sufficient to increase the male’s aggressiveness in the presence of an estrous female, although additional sensory input, such as the female’s movements, may be necessary to produce the full aggression-inducing effect.