How rat young govern the release of a maternal pheromone

We addressed the question of why the pheromone contained in the feces of the lactating rat first appears at 14 days postpartum, rather than earlier or later in the maternal episode. Our hypothesis was that the release of this pheromone is controlled by the young themselves, specifically by diet-induced changes in the acidity of their feces. Support for the hypothesis was advanced in a series of experiments showing that (a) lactating females consume the feces of their pups; (b) pup fecal-acidity decreases when, at 14 days of age, the pup begins to eat solid food; (c) this decrease is mirrored in the enteric pH of the mother; and (d) pheromonal release is either promoted or inhibited by experimentally manipulating the acidity of the mother's gut.