Table_4_Difference in the songs of paired and unpaired southern yellow-cheeked gibbon males (Nomascus gabriellae): social status or age?.docx

All gibbons (Primates: Hylobatidae) are well known for emitting loud vocalizations specific for species and sex. The songs of paired and unpaired male southern yellow-cheeked gibbons (Nomascus gabriellae) are characterized by the presence of staccato notes and multi-modulation phrases with two or more extremely rapid frequency modulations in the second note of each phrase. In addition, paired males also produce a coda vocalization, which is similar to the multi-modulation phrase of male calls but lacks the staccato notes and always occurs directly following the female great call as part of a pair-specific duet. The aim of this study was first to assess whether the songs of paired and unpaired males can be acoustically distinguished from one another and second, whether the coda vocalization differs from the multi-modulation phrase of the male call in paired males. To assess these issues, we analyzed 616 songs obtained from a long-term study of vocal development in 14 captive adult males (>7 years old), half of which were unpaired and significantly younger than paired subjects. For each song, we quantified nine acoustic features, for which we applied a suite of linear mixed effects models with social status as a fixed variable and age as a regression coefficient. This allowed us to compare (1) the structure of male calls (staccato notes and multi-modulation phrase) between paired and unpaired subjects, (2) the muti-modulation phrase of unpaired subjects to the coda vocalization of paired subjects, and (3) the multi-modulation phrase of paired males to the coda vocalization. We found that the male call of younger-unpaired subjects had a longer duration, broader frequency range, higher maximum frequency, and fewer staccato notes than their counterparts in paired subjects. The coda vocalization of older-paired males exhibited a larger number of frequency modulations than the multi-modulation phrase of all males. While the male call of younger-unpaired males differs from both the male call and the coda vocalization of older-paired males, further studies are necessary to disentangle the effects of age and pairing status.

所有长臂猿（灵长目：长臂猿科Hylobatidae）均以发出兼具物种与性别特异性的洪亮鸣叫声而广为人知。成对与未成对的南黄颊长臂猿（Nomascus gabriellae）雄性鸣唱，均以带有断音音节（staccato notes）以及多调制鸣句（multi-modulation phrases）为特征——每段鸣句的第二个音节中包含两次及以上极快速的频率调制。此外，成对雄性还会发出尾声鸣唱（coda vocalization），其结构与雄性鸣唱中的多调制鸣句相似，但缺失断音音节；且该尾声鸣唱始终紧随雌性大鸣唱出现，作为配对特异性二重唱的组成部分。本研究的首要目标为：其一，评估成对与未成对雄性的鸣唱能否通过声学特征实现区分；其二，探究成对雄性的尾声鸣唱，是否有别于其雄性鸣唱中的多调制鸣句。为解答上述问题，我们分析了616段鸣唱样本——这些样本取自一项针对14只圈养成年雄性长臂猿（年龄均大于7岁）鸣唱发育的长期研究，其中半数为未成对个体，且其年龄显著低于成对实验个体。针对每段鸣唱，我们量化了9项声学特征参数，并采用一系列线性混合效应模型（linear mixed effects models）开展分析：以社会地位作为固定变量，以年龄作为回归系数。借此我们得以开展三项对比：（1）成对与未成对个体的雄性鸣唱（含断音音节与多调制鸣句）结构差异；（2）未成对个体的多调制鸣句与成对个体的尾声鸣唱差异；（3）成对雄性的多调制鸣句与其尾声鸣唱差异。研究结果显示：与成对个体相比，未成对的年轻雄性的鸣唱时长更长、频率范围更广、最高频率更高，且断音音节数量更少。成对年长雄性的尾声鸣唱，其含有的频率调制次数多于所有雄性的多调制鸣句。尽管未成对的年轻雄性鸣唱，与成对年长雄性的雄性鸣唱及尾声鸣唱均存在差异，但仍需开展进一步研究，以厘清年龄与配对状态各自的影响效应。