Predation is an important ecological constraint that influences communication in animals. Fish respond to predators by adjusting their visual signaling behavior, but the responses in calling behavior in the presence of a visually detected predator are largely unknown. We hypothesize that fish will reduce visual and acoustic signaling including sound levels and avoid escalating fights in the presence of a predator. To test this we investigated dyadic contests in female croaking gouramis (Trichopsis vittata, Osphronemidae) in the presence and absence of a predator (Astronotus ocellatus, Cichlidae) in an adjoining tank. Agonistic behavior in T. vittata consists of lateral (visual) displays, antiparallel circling, and production of croaking sounds and may escalate to frontal displays. We analyzed the number and duration of lateral display bouts, the number, duration, sound pressure level, and dominant frequency of croaking sounds as well as contest outcomes. The number and duration of lateral displays decreased significantly in predator when compared with no-predator trials. Total number of sounds per contest dropped in parallel but no significant changes were observed in sound characteristics. In the presence of a predator, dyadic contests were decided or terminated during lateral displays and never escalated to frontal displays. The gouramis showed approaching behavior toward the predator between lateral displays. This is the first study supporting the hypothesis that predators reduce visual and acoustic signaling in a vocal fish. Sound properties, in contrast, did not change. Decreased signaling and the lack of escalating contests reduce the fish’s conspicuousness and thus predation threat.

中文翻译：

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捕食风险的声学和视觉适应：捕食者影响发声雌鱼的交流

捕食是影响动物交流的重要生态约束。鱼通过调整它们的视觉信号行为来对捕食者做出反应，但是在视觉检测到的捕食者存在的情况下呼叫行为的反应在很大程度上是未知的。我们假设鱼会减少视觉和听觉信号，包括声级，并避免在捕食者存在的情况下升级战斗。为了测试这一点，我们调查了在相邻的坦克中存在和不存在捕食者（Astronotus ocellatus，Cichlidae）的雌性呱呱叫（Trichopsis vittata，Osphronemidae）的二元比赛。T. vittata 的激动行为包括横向（视觉）显示、反平行盘旋和呱呱叫声，并可能升级为正面显示。我们分析了横向展示回合的数量和持续时间，呱呱叫的次数、持续时间、声压级和主要频率以及比赛结果。与没有捕食者的试验相比，捕食者的横向展示的数量和持续时间显着减少。每场比赛的声音总数同时下降，但声音特征没有明显变化。在有捕食者存在的情况下，二元竞赛在横向展示期间被决定或终止，并且从未升级到正面展示。gouramis 在横向展示之间表现出接近捕食者的行为。这是第一项支持捕食者减少有声鱼类的视觉和听觉信号这一假设的研究。相比之下，声音属性没有改变。