Katsu Noriko, Inami Kazuo, Yamada Kazunori
Graduate School of Human Sciences, The University of Osaka, 1-2 Yamadaoka, Suita, Osaka, Japan.
Primates. 2025 Sep 11. doi: 10.1007/s10329-025-01213-4.
Anthropogenic noise may affect the spectral and temporal structures of contact calls in wild non-human primates. However, most studies have compared groups living at varying distances from noise sources, while few have focused on the relationship between specific noise types and vocalizations at the individual level, which is necessary to examine vocal plasticity. We aimed to clarify the effects of background noise on the acoustic characteristics of coo calls of Japanese macaques on an individual basis; thus, we examined the effects of noise levels, behavioral context, and number of individuals in proximity on the duration and spectral measure of calls. We conducted focal observations of adult female Japanese macaques, and recorded coo calls and background noise levels. We analyzed 128 calls from nine subjects and found that the start and mean frequencies of coo calls were higher at higher noise levels. The call duration and frequency modulations were higher when the number of individuals in proximity was lower and the end frequency was higher during foraging and moving. These findings suggest that different factors affect the acoustic characteristics of the coo calls of Japanese macaques simultaneously. The most intense background noise sources were typically low-frequency sources that overlapped the frequency bands of the calls. Hence, they exerted a profound influence on call acoustics, which is consistent with the results of previous studies. Within-individual adjustments to ambient noise indicate vocal plasticity, enabling efficient signal transmission to the receiver.
人为噪声可能会影响野生非人类灵长类动物接触叫声的频谱和时间结构。然而，大多数研究比较的是生活在距噪声源不同距离处的群体，而很少有研究关注个体层面特定噪声类型与发声之间的关系，而这对于研究发声可塑性是必要的。我们旨在阐明背景噪声对日本猕猴咕咕叫声声学特征的个体影响；因此，我们研究了噪声水平、行为背景以及附近个体数量对叫声持续时间和频谱测量的影响。我们对成年雌性日本猕猴进行了焦点观察，并记录了咕咕叫声和背景噪声水平。我们分析了来自9只猕猴的128次叫声，发现噪声水平越高，咕咕叫声的起始频率和平均频率越高。当附近个体数量较少时，叫声持续时间和频率调制较高，且在觅食和移动时结束频率较高。这些发现表明不同因素会同时影响日本猕猴咕咕叫声的声学特征。最强烈的背景噪声源通常是与叫声频段重叠的低频源。因此，它们对叫声声学产生了深远影响，这与先前研究的结果一致。个体对环境噪声的调整表明发声具有可塑性，能够实现向接收者的高效信号传输。
