Body postures are essential in animal behavioural repertoires and their communicative role has been assessed in a wide array of taxa and contexts. Some body postures function as amplifiers, a class of signals that increase the detection likelihood of other signals. While foraging on the ground, bonobos (Pan paniscus) can adopt different crouching postures exposing more or less of their genital area. To our knowledge, their potential functional role in the sociosexual life of bonobos has not been assessed yet. Here we show, by analysing more than 2,400 foraging events in 21 captive bonobos, that mature females adopt a rear-exposing posture (forelimb-crouch) and do so significantly more often when their anogenital region is swollen than during the non-swollen phase. In contrast, mature males almost completely avoid this posture. Moreover, this strong difference results from a diverging ontogeny between males and females since immature males and females adopt the forelimb-crouch at similar frequencies. Our findings suggest that the forelimb-crouch posture may play a communicative role of amplification by enhancing the visibility of female sexual swellings, a conspicuous signal that is very attractive for both males and females. Given the high social relevance of this sexual signal, our study emphasizes that postural signalling in primates probably deserves more attention, even outside of reproductive contexts.

身体姿势在动物行为剧目中是必不可少的，它们的交际作用已在广泛的分类群和环境中得到评估。一些身体姿势起到放大器的作用，这是一类增加其他信号检测可能性的信号。在地面觅食时，倭黑猩猩（Pan paniscus）可以采取不同的蹲姿，或多或少地暴露出它们的生殖器区域。据我们所知，它们在倭黑猩猩社会性生活中的潜在功能尚未得到评估。在这里，我们通过分析 21 只圈养倭黑猩猩的 2,400 多次觅食事件表明，成年雌性倭黑猩猩采用后暴露姿势（前肢蹲伏) 并且当他们的肛门生殖器区域肿胀时比非肿胀阶段更频繁地这样做。相比之下，成熟的雄性几乎完全避免这种姿势。此外，这种强烈的差异源于雄性和雌性之间的个体发育差异，因为未成熟的雄性和雌性以相似的频率采用前肢蹲伏。我们的研究结果表明，前肢蹲伏姿势可能通过增强女性性肿胀的可见度而起到放大交流的作用，这是一个对男性和女性都非常有吸引力的显着信号。鉴于这种性信号的高度社会相关性，我们的研究强调灵长类动物的姿势信号可能值得更多关注，即使是在生殖环境之外。