The adaptive function of male masturbation is still poorly understood, despite its high prevalence in humans and other animals. In non-human primates, male masturbation is most frequent among anthropoid monkeys and apes living in multimale-multifemale groups with a promiscuous mating system. In these species, male masturbation may be a non-functional by-product of high sexual arousal or be adaptive by providing advantages in terms of sperm competition or by decreasing the risk of sexually transmitted infections. We investigated the possible functional significance of male masturbation using behavioral data collected on 21 free-ranging male rhesus macaques (Macaca mulatta) at the peak of the mating season. We found some evidence that masturbation is linked to low mating opportunities: regardless of rank, males were most likely to be observed masturbating on days in which they were not observed mating, and lower-ranking males mated less and tended to masturbate more frequently than higher-ranking males. These results echo the findings obtained for two other species of macaques, but contrast those obtained in red colobus monkeys (Procolobus badius) and Cape ground squirrels (Xerus inauris). Interestingly, however, male masturbation events ended with ejaculation in only 15% of the observed masturbation time, suggesting that new hypotheses are needed to explain masturbation in this species. More studies are needed to establish whether male masturbation is adaptive and whether it serves similar or different functions in different sexually promiscuous species.

中文翻译：

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交配活动和优势等级对散养雄性恒河猴雄性自慰的影响


尽管男性自慰在人类和其他动物中普遍存在，但其适应性功能仍然知之甚少。在非人类灵长类动物中，雄性自慰在类人猿和猿类中最为常见，这些类人猿和猿生活在具有混杂交配系统的多雄多雌群体中。在这些物种中，男性手淫可能是高性唤起的非功能性副产品，或者通过提供精子竞争方面的优势或降低性传播感染的风险而具有适应性。我们利用 21 只自由放养的雄性恒河猴 (Macaca mulatta) 在交配季节高峰期收集的行为数据，研究了雄性自慰可能的功能意义。我们发现了一些证据，表明手淫与低交配机会有关：无论等级如何，雄性最有可能在没有观察到交配的日子里观察到自慰，而地位较低的雄性比地位较高的雄性交配较少，并且倾向于更频繁地手淫- 男性排名。这些结果与其他两种猕猴的研究结果相呼应，但与红疣猴（Procolobus badius）和海角地松鼠（Xerus inauris）的研究结果形成鲜明对比。然而有趣的是，男性自慰事件仅在观察到的自慰时间的 15% 内以射精结束，这表明需要新的假设来解释该物种的自慰。需要更多的研究来确定男性自慰是否具有适应性，以及它在不同性乱物种中是否具有相似或不同的功能。