Environmental and endocrine factors influencing annual changes in sexual potency in primates

Abstract

(1) Available data on breeding seasonality in primates are summarized. (2) When intact female rhesus monkeys, whose Fallopian tubes had been ligated to prevent pregnancy, were paired with intact males in a laboratory in London, the timing of the annual increase (autumn) in mating activity was closely similar to that in India. (3) When ovariectomized, estrogentreated females were paired with intact males in a laboratory in Atlanta, where the photoperiod was strictly controlled, the annual increase in mating activity persisted during the first year, although it was less well-circumscribed. (4) During the second year in a fixed photoperiod, in a sham-castrated group, the annual increase in sexual activity virtually disappeared. (5) During the second year in a fixed photoperiod, however, in a castrated, testosterone-treated group, a brief increase in sexual activity occurred at the expected time. (6) When ovariectomized, estrogen-treated female rhesus monkeys were paired with castrated, testosterone-treated males in a laboratory in London, the seasonal increase in sexual activity occurred at the expected time, indicating that it was not entirely dependent upon pituitary activation of the gonads. (7) Seasonal factors operating in the female are also considered.