Male counter strategies to cyclic shifts

Human female fertility varies over the menstrual cycle. The likelihood that a single act of intercourse will result in conception is greatest in the days preceding ovulation. At this time, women are more attractive and are more driven to enhance their attractiveness. Androphilic women become more interested in men who are not their primary partner, and their preference for physically and behaviorally feminine men decreases. Because men who are women's primary partners risk desertion or (if their partner engages in short-term sexual relationships with other men) investing in biologically unrelated offspring, they have likely experienced selection pressure to deploy counterstrategies that mitigate the effects of female menstrual cycle shifts. These counterstrategies may include changes to a man's sexual desire, his jealousy and mate-guarding behavior, and his propensity to compete with sexual rivals.