In mammals, allogrooming is prominent in forming and maintaining social and cooperative relationships. Yet an animal's social time is constrained, which may limit its access to a large number of partners. Dunbar (1993, Behavioral and Brain Sciences, 16 (4), 681–694) proposed that human polyadic conversations, which allow access to several social partners simultaneously, evolved as a form of social grooming to circumvent this time constraint. In nonhuman primates, polyadic grooming (PG), in contrast to dyadic grooming, may similarly be a time-efficient way to maintain weak social relationships with many partners which can be important for group level cooperation. It remains unknown whether PG is used to fulfil specific cooperative needs by accessing numerous weakly bonded partners and increasing the number of partners accessed per unit of time. We compared the use and effect of PG between chimpanzees, Pan troglodytes, which are highly territorial and collaborative (especially males), and bonobos, Pan paniscus, which are less territorial and collaborative and in which females are the main co-operators. We carried out focal grooming observations in one bonobo and two chimpanzee communities in the wild. As predicted, chimpanzees engaged in more PG than bonobos. Surprisingly, males engaged in PG more than females in both species. While chimpanzees accessed more partners per minute of grooming than bonobos via dyadic grooming, PG increased the number of partners accessed per minute only in bonobos. Finally, chimpanzees primarily used PG with individuals who were close in rank and frequent grooming partners, whereas bonobos used PG with individuals who were distant in rank, close party associates and frequent grooming partners. We suggest that bonobo males use PG to enhance conspecific social tolerance and mate choice. The overall higher rate of PG in chimpanzees suggests that between-group competition may promote polyadic affiliation, which possibly reinforces group cohesion and coordination. © 2020 The Authors

中文翻译：

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多元梳理的不同用途及其对野生黑猩猩和倭黑猩猩获得社会伙伴的影响

在哺乳动物中，同种修饰在形成和维持社会和合作关系方面很突出。然而，动物的社交时间是有限的，这可能会限制它与大量伙伴的接触。Dunbar (1993, Behavioral and Brain Sciences, 16 (4), 681–694) 提出，允许同时接触多个社交伙伴的人类多元对话进化为一种社交修饰形式，以规避这种时间限制。在非人类灵长类动物中，与二元梳理相反，多元梳理 (PG) 可能同样是一种节省时间的方式，可以与许多伙伴保持薄弱的社会关系，这对于群体层面的合作可能很重要。PG 是否用于通过访问众多弱结合合作伙伴和增加单位时间内访问的合作伙伴数量来满足特定的合作需求仍然未知。我们比较了 PG 在具有高度领土性和协作性（尤其是雄性）的黑猩猩 Pan troglodytes 和不具有领土性和协作性且雌性是主要合作者的倭黑猩猩 Pan paniscus 之间的使用和效果。我们在野外的一只倭黑猩猩和两只黑猩猩群落中进行了重点梳理观察。正如预测的那样，黑猩猩比倭黑猩猩从事更多的 PG。令人惊讶的是，在这两个物种中，男性比女性更多地参与 PG。虽然黑猩猩通过二元梳理每分钟接触到的伴侣比倭黑猩猩多，但 PG 只增加了每分钟接触倭黑猩猩的伴侣数量。最后，黑猩猩主要将 PG 用于等级相近且经常梳理毛发的个体，而倭黑猩猩则将 PG 用于等级相距较远的个体，亲密的派对伙伴和频繁的美容伙伴。我们建议倭黑猩猩雄性使用 PG 来增强同种社会容忍度和配偶选择。黑猩猩整体较高的 PG 率表明，群体间的竞争可能会促进多元从属关系，这可能会加强群体的凝聚力和协调。© 2020 作者