Data from: Overlapping vocalizations produce far-reaching choruses: a test of the signal enhancement hypothesis

Many animals gather in large groups to mate. When these animals produce sexual signals, their signals may overlap. The signal enhancement hypothesis proposes that overlapping signals exhibit enhanced transmission properties, increasing the active space and potency of the signal. We tested this hypothesis using multi-speaker playback to simulate a chorus of explosively breeding Neotropical Yellow Toads (Incilius luetkenii). We varied the number of simulated males and the frequency of their vocalizations and we re-recorded the choruses at different distances through this species’ native habitat in Costa Rica. Our results support the signal enhancement hypothesis: transmission distance increased with the number of simultaneous calls. Call frequency varies inversely with body size in many animals, including Yellow Toads, and our results reveal that the signal enhancement effect of overlapping calls is heightened when the calls are low in frequency (i.e. a chorus of large-bodied animals) compared to medium or high frequency (i.e. a chorus of smaller-bodied animals). Our findings represent the first experimental demonstration of chorus-level signal enhancement in the vocalizations of vertebrates.

诸多动物会集结成庞大群体以完成交配行为。当这类动物发出性信号时，信号之间可能发生重叠。信号增强假说（signal enhancement hypothesis）提出，重叠信号具备更优异的传播特性，可扩大信号的有效作用范围与传递效能。本研究采用多扬声器回放（multi-speaker playback）技术，模拟爆发式繁殖的新热带区黄色蟾蜍（Incilius luetkenii）的鸣唱群，对该假说进行了实验验证。我们通过调整模拟雄性个体的数量及其鸣唱频率，并在哥斯达黎加该物种的原生栖息地中，于不同距离处重新录制鸣唱群的声学信号。本研究结果支持信号增强假说：同步鸣唱的个体数量越多，信号的传播距离越远。在包括黄色蟾蜍在内的诸多动物类群中，鸣唱频率与体型呈负相关；本研究结果进一步显示，相较于中等或高频鸣唱（对应体型较小的动物鸣唱群），低频鸣唱（对应体型较大的动物鸣唱群）时，重叠鸣唱的信号增强效应会更为显著。本研究的发现首次在脊椎动物的鸣唱行为中，通过实验证实了鸣唱群层面的信号增强效应。