Hedwig Daniela, Poole Joyce, Granli Petter
Elephant Listening Project, K. Lisa Yang Center for Conservation Bioacoustics, Cornell Lab of Ornithology, Cornell University, Ithaca, NY 14850, USA.
Elephant Voices, 3236 Sandefjord, Norway.
Animals (Basel). 2021 Oct 27;11(11):3071. doi: 10.3390/ani11113071.
The social complexity hypothesis (SCH) for communication states that the range and frequency of social interactions drive the evolution of complex communication systems. Surprisingly, few studies have empirically tested the SHC for vocal communication systems. Filling this gap is important because a co-evolutionary runaway process between social and vocal complexity may have shaped the most intricate communication system, human language. We here propose the African elephant . as an excellent study system to investigate the relationships between social and vocal complexity. We review how the distinct differences in social complexity between the two species of African elephants, the forest elephant and the savanna elephant , relate to repertoire size and structure, as well as complex communication skills in the two species, such as call combination or intentional formant modulation including the trunk. Our findings suggest that may contradict the SCH, as well as other factors put forth to explain patterns of vocal complexity across species. We propose that life history traits, a factor that has gained little attention as a driver of vocal complexity, and the extensive parental care associated with a uniquely low and slow reproductive rate, may have led to the emergence of pronounced vocal complexity in the forest elephant despite their less complex social system compared to the savanna elephant. Conclusions must be drawn cautiously, however. A better understanding of vocal complexity in the genus will depend on continuing advancements in remote data collection technologies to overcome the challenges of observing forest elephants in their dense rainforest habitat, as well as the availability of directly comparable data and methods, quantifying both structural and contextual variability in the production of rumbles and other vocalizations in both species of African elephants.
用于交流的社会复杂性假说（SCH）指出，社会互动的范围和频率推动了复杂交流系统的进化。令人惊讶的是，很少有研究对语音交流系统的社会复杂性假说进行实证检验。填补这一空白很重要，因为社会复杂性和语音复杂性之间的共同进化失控过程可能塑造了最复杂的交流系统——人类语言。我们在此提出，非洲象是研究社会复杂性与语音复杂性之间关系的绝佳研究系统。我们回顾了非洲象的两种——森林象和草原象——在社会复杂性上的显著差异如何与发声库的大小和结构相关，以及这两个物种的复杂交流技能，如叫声组合或包括象鼻在内的有意共振峰调制。我们的研究结果表明，这可能与社会复杂性假说以及其他用来解释跨物种语音复杂性模式的因素相矛盾。我们提出，生活史特征——作为语音复杂性驱动因素很少受到关注的一个因素——以及与极低且缓慢的繁殖率相关的广泛亲代抚育，可能导致了森林象尽管与草原象相比其社会系统较不复杂，但仍出现了显著的语音复杂性。然而，得出结论必须谨慎。要更好地理解象属的语音复杂性，将取决于远程数据收集技术的持续进步，以克服在茂密雨林栖息地观察森林象的挑战，以及是否有直接可比的数据和方法，来量化非洲象两个物种发出的隆隆声和其他叫声在结构和情境上的变异性。
