Nadler R D
Arch Sex Behav. 1977 Nov;6(6):457-75. doi: 10.1007/BF01541151.
Opposite-sex pairs of orangutans were tested for sexual behavior during the intermenstrual period of the female. The male orangutan was the primary initiator of sexual interactions and initiated copulation forcefully on a daily basis, irrespective of female resistance. However, although single copulations occurred daily, copulations beyond the first occurred most frequently during midcycle. Other evidence of cyclicity in behavior was the midcycle decrease in female avoidance of the male and increased grooming, proceptivity, and masturbation by the female. Comparative analysis suggests that differences in sexual cyclicity among the great ape species are related to interspecies differences in sexual assertiveness of males and females. Sexual activity in the cycle is relatively brief when the female controls mating, more prolonged when the male is in control. This finding in man's closest taxonomic affiliates suggests that similar social factors may also influence the distribution of sexual interactions in the human cycle.
在雌性猩猩的月经间期，对异性配对的猩猩进行了性行为测试。雄性猩猩是性互动的主要发起者，每天都会强行发起交配，而不顾雌性的抗拒。然而，尽管每天都会发生单次交配，但首次交配之后的交配最常发生在周期中期。行为周期性的其他证据是，雌性在周期中期减少了对雄性的回避，增加了梳理毛发、主动求爱和自慰行为。比较分析表明，类人猿物种之间性周期的差异与雄性和雌性在性主动性方面的种间差异有关。当雌性控制交配时，周期中的性活动相对短暂；当雄性控制交配时，则会延长。在人类最近的分类亲属中发现的这一现象表明，类似的社会因素可能也会影响人类性互动在周期中的分布。
