Sexual Attractiveness and Receptivity in Rhesus Monkeys

Abstract

THE catarrhine monkeys and the apes alone among animals have a clearly defined menstruation with a cycle lasting about 30 days. They do not show well-circumscribed periods of oestrus (heat), but will copulate throughout the cycle. This has led to the idea that the great development of neocortical mechanisms in the primate has resulted in an emancipation of its brain from the influence of gonadal steroids¹. Earlier work in both the rhesus monkey^2,3 and the chimpanzee^4–6, however, has indicated that the level of sexual interaction shows some variation with the phases of the menstrual cycle. Furthermore, studies of the rhesus monkey^7,8 have shown that well marked rhythms of mounting behaviour by males occur in relation to the menstrual cycles of their female partners. These rhythms are abolished by bilateral ovariectomy, and so endocrine mechanisms in primate sexual behaviour seem to have been underestimated⁹.