Abstract

Reciprocity is a prominent explanation for cooperation between non-kin. Studies designed to demonstrate reciprocity often focus on direct reciprocity in the timescale of minutes to hours, whereas alternative mechanisms like generalized reciprocity and the possibility of reciprocation over longer timescales of months and years are less often explored. Using a playback experiment, we tested for evidence of direct and generalized reciprocity across short and longer timescales. We examined the exchange of grooming for coalitionary support between unrelated female rhesus macaques in a population with a complete genetic pedigree. Females that received grooming were not more responsive to calls for coalitionary support from unrelated female group mates compared to control females that received agonism or no interaction — even when the call belonged to a females’ most recent grooming partner. Similarly, females were not more responsive to calls for support from their most frequent unrelated grooming partner of the last two years, nor if they received large amounts of grooming from all other females in their group. We interpret these results as an absence of evidence for direct or generalized reciprocity on any timescale in the exchange of grooming for coalitionary support in rhesus macaques. If grooming is exchanged for support in this population, it is with an intensity below our ability to detect it or over a longer timescale than we examined. We propose by-product explanations may also be at play and highlight the importance of investigating multiple mechanisms when testing apparently cooperative behaviors.

Significance statement

The receipt of help can make some animals more likely to provide help in return, whether it be a singular act, or many acts accumulated over months. Similarly, the receipt of help, be it one act of aid, or a group’s worth of help over time, can make some animals more likely to pay help forward to others. Studies on Old World monkeys suggest females may give grooming and in return receive aid in future physical conflicts. Using a playback experiment, we found female rhesus macaques were not more responsive to calls for intervention in a simulated conflict after being groomed by unrelated females, even if the calling combatant was her most recent, or a long-time grooming partner. Our results suggest females in our study population may be receiving benefits other than support in conflicts for the grooming they provide.

中文翻译：

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没有证据表明，在短期或长期内，通过无关恒河猴的直接或普遍互惠，可以用梳理毛发换取联合支持

摘要

互惠是非亲属之间合作的一个突出解释。旨在证明互惠的研究通常集中在几分钟到几小时的时间尺度上的直接互惠，而其他机制，如广义互惠和在更长的时间尺度上的互惠的可能性，则很少探索。使用回放实验，我们测试了在短期和较长时间尺度上直接和广义互惠的证据。我们检查了在具有完整遗传谱系的人群中，不相关的雌性恒河猴之间为联合支持而进行的梳理交流。与接受激动或没有互动的对照女性相比，接受梳理的女性对来自不相关的女性群体的联合支持的呼声并没有更敏感的反应——即使该呼叫属于女性最近的梳理伴侣。同样，在过去两年中，女性对她们最频繁的无关梳理伴侣的支持呼声没有更敏感的反应，也没有从他们小组中的所有其他女性那里得到大量的梳理。我们将这些结果解释为缺乏任何时间尺度上直接或普遍互惠的证据，以换取恒河猴的联合支持。如果在这个人群中以修饰换取支持，它的强度低于我们检测它的能力，或者在比我们检查的更长的时间范围内。

意义陈述

接受帮助可以使一些动物更有可能提供帮助作为回报，无论是单一的行为，还是数月来积累的许多行为。同样，接受帮助，无论是一次帮助，还是随着时间的推移一个群体的帮助，都可以使一些动物更有可能向其他动物提供帮助。对旧大陆猴子的研究表明，雌性可能会进行梳理毛发，并在未来的身体冲突中获得帮助。使用回放实验，我们发现雌性恒河猴在被无关的雌性修饰后，对干预模拟冲突的呼声并没有更敏感的反应，即使呼唤的战斗者是她最近的或长期的修饰伙伴。我们的研究结果表明，我们研究人群中的女性可能会获得好处，而不是在冲突中为她们提供的修饰提供支持。