Intergroup competition is a widespread phenomenon across taxa and groups typically compete over access to limited resources, such as food and mates. Such competition may be quantified by changes in individuals' behavioral and physiological status in response to intergroup encounters (IGEs). Bonobos, one of our closest living relatives, are often regarded as xenophilic and exhibit high tolerance towards out-group individuals. This tolerance between groups may still be accompanied by intergroup competition over resources. We hereby compared variation in aggression rates and urinary cortisol levels of bonobos during and outside contexts of IGEs in the Kokolopori Bonobo Reserve and investigated whether food and mate availability influenced males' and females' aggression and cortisol levels, when controlling for dominance rank and the number of individuals present. We found that although females had higher aggression rates and urinary cortisol levels during than outside contexts of IGEs, these increases were not related to food availability or changes in between-group dynamics when maximally tumescent females were present, rather than absent. Furthermore, males showed higher aggression rates and urinary cortisol levels during than outside contexts of IGEs. However, males' responses during IGEs were not related to the presence of maximally tumescent females and food availability. Taken together, while competition intensified during seemingly tolerant IGEs in bonobos, such competition was unrelated to short-term changes in food and mate availability. Despite physical and physiological costs of aggression, bonobos associate with out-group individuals frequently and for extended periods. This suggests potential benefits of bonobo intergroup associations.

群际竞争是跨类群的普遍现象，群体通常会争夺对有限资源（例如食物和配偶）的获取。这种竞争可以通过个体对群际相遇 (IGE) 的行为和生理状态的变化来量化。倭黑猩猩是我们在世最亲近的亲属之一，通常被认为是外来者，对外群个体表现出很高的容忍度。群体之间的这种容忍可能仍然伴随着群体间对资源的竞争。我们在此比较了 Kokolopori 倭黑猩猩保护区 IGE 环境中和外部倭黑猩猩的攻击率和尿皮质醇水平的变化，并调查了食物和配偶的可用性是否影响了雄性和雌性的攻击性和皮质醇水平，当控制优势等级和存在的个体数量时。我们发现，尽管女性在 IGE 的外部环境中具有更高的攻击率和尿皮质醇水平，但这些增加与食物供应或组间动态变化无关，当最大肿胀的女性存在而不是不存在时。此外，与 IGE 的外部环境相比，男性表现出更高的攻击率和尿皮质醇水平。然而，雄性在 IGE 期间的反应与最大肿胀雌性的存在和食物供应无关。综上所述，虽然倭黑猩猩看似耐受的 IGE 期间竞争加剧，但这种竞争与食物和配偶可用性的短期变化无关。尽管攻击行为会造成身体和生理上的代价，倭黑猩猩经常和长期与群体外的人交往。这表明倭黑猩猩群际关联的潜在好处。