When the benefits of interacting with out-group members exceed the associated costs, social groups may be expected to be tolerant towards each other. However, in many species exhibiting intergroup tolerance, the nature of benefits gained from intergroup encounters remains unclear. We investigated the potential costs and benefits associated with intergroup associations in bonobos, a species with varying degrees of intergroup tolerance, by testing whether these associations conferred energetic benefits to participants under different socioecological contexts and whether the consequences of these associations substantially differed from within-group competition. We used measures of socioecological factors (fruit abundance and group size), feeding and ranging behaviors, and a physiological marker of energy balance (urinary c-peptide of insulin) collected over a 19-month period from two neighboring wild communities in the Kokolopori Bonobo Reserve, Democratic Republic of the Congo. We found that intergroup associations were not related to individuals’ energy balance, but they were related to variations in individuals’ ranging and feeding behavior. Specifically, bonobos traveled longer distances, visited larger fruit patches, and increased the time spent feeding on fruits on days they associated with the neighboring group. These adaptations in feeding behavior may be strategies to offset the energetic costs of increased travel distances. In the absence of obvious energetic benefits and with clear strategies employed to offset energetic costs, it is likely that intergroup associations in bonobos provide benefits unrelated to energy acquisition, such as social benefits. Our study sheds light on the potential incentives promoting social networks to extend beyond and across groups in a tolerant species. Intergroup encounters can be energetically costly due to increased competition over resources. Yet, some species associate with out-group individuals for extended periods of time when the benefits of participating in these associations exceed the potential costs. Bonobos, a species exhibiting intergroup tolerance, modified their feeding behavior during intergroup associations by feeding on larger fruit patches and increasing their time spent feeding on fruits, likely to offset energetic costs of increased travel distances. As results, individuals’ energy balance was not related with intergroup associations. The employment of such strategies in addition to the absence of clear energetic benefits suggests that intergroup associations in bonobos provide social rather than ecological benefits.

中文翻译：

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在一起更好吗？群际关联如何影响野生倭黑猩猩的能量平衡和摄食行为

当与外群体成员互动的收益超过相关成本时，社会群体可能会相互宽容。然而，在许多表现出群际耐受性的物种中，从群际相遇中获得的利益的性质仍不清楚。我们通过测试这些关联是否为不同社会生态环境下的参与者带来能量收益以及这些关联的后果是否与组内有显着差异，调查了与倭黑猩猩（一种具有不同组间容忍度的物种）中的组间关联相关的潜在成本和收益竞赛。我们使用了社会生态因素（水果丰度和群体规模）、喂养和范围行为的措施，以及在 19 个月内从刚果民主共和国科科洛波里倭黑猩猩保护区的两个邻近野生群落收集的能量平衡生理标志物（胰岛素的尿液 c 肽）。我们发现群际关联与个体的能量平衡无关，但与个体的测距和进食行为的变化有关。具体来说，倭黑猩猩旅行的距离更长，访问了更大的水果块，并增加了在与邻近群体相关的日子里吃水果的时间。这些喂养行为的适应可能是抵消增加旅行距离的能量成本的策略。在缺乏明显的能量收益并且采用明确的策略来抵消能量成本的情况下，倭黑猩猩的群体间协会很可能提供与能源获取无关的利益，例如社会利益。我们的研究揭示了促进社交网络扩展到宽容物种群体之外的潜在激励因素。由于对资源的竞争加剧，群际遭遇可能会耗费大量精力。然而，当参与这些协会的好处超过潜在成本时，一些物种会与外群个体长期交往。倭黑猩猩是一种表现出群际耐受性的物种，通过以较大的水果块为食并增加以水果为食的时间，在群际交往期间改变了它们的进食行为，这可能抵消增加旅行距离的能量成本。结果，个体的能量平衡与群际交往无关。除了缺乏明显的能量收益外，使用此类策略表明倭黑猩猩的群际交往提供了社会效益而不是生态效益。