Mammals living in stable social groups often mitigate the costs of group living through the formation of social bonds and cooperative relationships. The neuropeptide hormone oxytocin (OT) is proposed to promote both bonding and cooperation although only a limited number of studies have investigated this under natural conditions. Our aim was to assess the role of OT in bonding and cooperation in male Barbary macaques (Macaca sylvanus). First, we tested for an effect of affiliation - grooming and triadic male-infant-male interactions - with bond and non-bond partners on urinary OT levels. Second, we tested whether grooming interactions (and thus increased OT levels) increase a male's general propensity to cooperate in polyadic conflicts. We collected >4000 h of behavioral data on 14 adult males and measured OT levels from 139 urine samples collected after affiliation and non-social control periods. Urinary OT levels were higher after grooming with any partner. By contrast, OT levels after male-infant-male interactions with any partner or with bond partners were not different from controls but were higher after interactions with non-bond partners. Previous grooming did not increase the likelihood of males to support others in conflicts. Collectively, our results support research indicating that OT is involved in the regulation of adult affiliative relationships. However, our male-infant-male interaction results contradict previous studies suggesting that it is affiliation with bond rather than non-bond partners that trigger the release of OT. Alternatively, OT levels were elevated prior to male-infant-male interactions thus facilitating interaction between non-bond partners. The lack of an association of grooming and subsequent support speaks against an OT linked increase in the general propensity to cooperate.

中文翻译：

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雄性巴巴里猕猴之间亲和相互作用后催产素增加。

生活在稳定的社会群体中的哺乳动物通常通过形成社会纽带和合作关系来减轻群体生活的成本。提出了神经肽激素催产素（OT）促进结合和合作，尽管只有有限的研究在自然条件下对此进行了研究。我们的目的是评估OT在雄性巴巴里猕猴（Macaca sylvanus）的结合与合作中的作用。首先，我们测试了有结合和无结合伴侣对尿中OT含量的亲缘关系（梳理和三联体男女婴互动）的影响。其次，我们测试了修饰互动（从而增加了OT水平）是否增加了男性多发性冲动中合作的一般倾向。我们收集了> 在14个成年男性身上有4000小时的行为数据，并在从属和非社会控制期后从139个尿液样本中测量了OT水平。与任何伴侣进行梳理后，尿中OT水平升高。相比之下，在与任何伴侣或有性伴侣进行男婴间相互作用后，OT水平与对照组无差异，但在与非有性伴侣相互作用后升高。以前的修饰并没有增加男性在冲突中支持他人的可能性。总体而言，我们的结果支持研究表明OT参与了成人亲属关系的调节。但是，我们的男女婴互动结果与先前的研究相矛盾，这表明触发OT释放的原因是其具有联系而不是非联系伴侣。或者，在男性-婴儿-男性相互作用之前，OT水平升高，从而促进了非结合伴侣之间的相互作用。缺乏梳理和后续支持的联系，说明旧约相关的合作倾向普遍增加。