Many theories and communication models developed from terrestrial studies focus on a simple dyadic exchange between a sender and receiver. During social interactions, the “frequency code” hypothesis suggests that frequency characteristics of vocal signals can simultaneously encode for static signaler attributes (size or sex) and dynamic information, such as motivation or emotional state. However, the additional presence of a bystander may result in a change of signaling behavior if the costs and benefits associated with the presence of this bystander are different from that of a simple dyad. In this study, two common humpback whale social calls (“wops” and “grumbles”) were tested for differences related to group social behavior and the presence of bystanders. “Wop” parameters were stable with group social behavior, but were emitted at lower (14 dB) levels in the presence of a nearby singing whale compared to when a singing whale was not in the area. “Grumbles” were emitted at lower (30–39 Hz) fundamental frequencies in affiliative compared to non-affiliative groups and, in the presence of a nearby singing whale, were also emitted at lower (14 dB) levels. Vocal rates did not significantly change. The results suggest that, in humpbacks, the frequency in certain sound types relates to the social behavior of the vocalizing group, implying a frequency code system. The presence of a nearby audible bystander (a singing whale) had no effect on this frequency code, but by reducing their acoustic level, the signal-to-noise ratio at the singer would have been below 0, making it difficult for the singer to audibly detect the group.Significance statementThe frequency, duration, and amplitude parameters of humpback whale social vocalizations were tested between different social contexts: group social behavior (affiliating versus non-affiliating), the presence of a nearby singing whale, and the presence of a nearby non-singing group. “Grumbles” (commonly heard low-frequency unmodulated sounds) frequencies were lower in affiliating groups compared to non-affiliating groups, suggesting a change in group motivation (such as levels of aggression). “Wop” (another common sound type) structure (frequency and duration) was similar in affiliating and non-affiliating groups. In the presence of an audible bystander (a singing whale), both sound types were emitted at similar rates, but much lower amplitudes (14 dB), vastly reducing the detectability of these sounds by the singer. This suggests that these groups were acoustically avoiding the singing whale. They did not, however, acoustically respond to the presence of a nearby non-singing group.

中文翻译：

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座头鲸声音参数随社会背景的变化：考虑旁观者的影响

从地面研究发展而来的许多理论和通信模型都侧重于发送者和接收者之间的简单二元交换。在社交互动过程中，“频率代码”假设表明，声音信号的频率特征可以同时编码静态信号属性（大小或性别）和动态信息，如动机或情绪状态。但是，如果与旁观者的存在相关的成本和收益与简单的二元组不同，那么旁观者的额外存在可能会导致信号行为的变化。在这项研究中，测试了两种常见的座头鲸社交呼叫（“wops”和“grumbles”）与群体社交行为和旁观者存在相关的差异。“Wop”参数随着群体社会行为而稳定，但与唱歌的鲸鱼不在该区域时相比，在附近有唱歌的鲸鱼的情况下以较低（14 dB）的水平发射。与非附属团体相比，附属团体以较低（30-39 Hz）的基本频率发出“抱怨”，并且在附近有唱歌的鲸鱼存在的情况下，也以较低（14 dB）的水平发出。声频没有显着变化。结果表明，在座头鲸中，某些声音类型的频率与发声群体的社会行为有关，这意味着频率代码系统。附近可听见的旁观者（唱歌的鲸鱼）的存在对这个频率代码没有影响，但通过降低他们的声级，歌手的信噪比会低于 0，使得歌手难以有声检测组。意义陈述的频率，座头鲸社交发声的持续时间和幅度参数在不同的社会背景下进行了测试：群体社会行为（附属与非附属）、附近唱歌鲸的存在以及附近非唱歌群体的存在。与非附属团体相比，附属团体的“抱怨”（通常听到的低频未调制声音）频率较低，这表明团体动机发生了变化（例如攻击性水平）。“Wop”（另一种常见的声音类型）结构（频率和持续时间）在附属组和非附属组中相似。在旁观者（唱歌的鲸鱼）可以听到的情况下，两种声音类型以相似的速率发出，但幅度要低得多（14 dB），大大降低了歌手对这些声音的可检测性。这表明这些群体在声学上避开了唱歌的鲸鱼。然而，他们并没有对附近没有唱歌的团体的存在做出声学反应。