Female mice pheromones may excite a male mouse to mate immediately. In addition to producing instinctive behavioral responses, pheromones can also produce changes in an animal's physiology, spurring the onset of puberty or bringing on estrus. Pheromones used by animals, such as cats and dogs, to mark territory can convey information about an animal's species, gender, age, social and reproductive status, size, and even when it was last in the area. But can humans communicate via chemicals, too? In the 1970s Martha McClintock showed that the menstrual cycles of women living closely together in dormitories tended to become synchronized, an effect thought by some to be mediated by pheromones. Despite such evidence, no pheromone receptors have yet been found in humans.