Data from: The signal in noise: acoustic information for soundscape orientation in two North American treefrogs

Diverse animals use environmental sounds to orient in ecological soundscapes. Yet, we know little about how acoustic information use drives behavioral decisions to orient. While the sound generated by frog choruses functions as noise that impairs signal reception by listeners in the aggregation, it can also serve as an informative ecological signal that allows other individuals to orient toward and localize active breeding aggregations. Here, we investigated the acoustic cues that elicit orientation toward the sound of a chorus in green treefrogs (Hyla cinerea) and Cope’s gray treefrogs (H. chrysoscelis). We measured phonotaxis behavior of gravid females in response to playbacks of natural choruses and artificial choruses that differed in the types of acoustic information present. Females of both species oriented to natural choruses and to artificial choruses that contained information on the actual timing and temporal structure of individual calls embedded in the sound of the chorus. Artificial choruses with the time-averaged frequency spectrum and amplitude-modulation spectrum of natural choruses, but lacking information on the timing and temporal structure of individual calls, did not elicit positive phonotaxis. Our results indicate that temporal information from individual calls in the din of chorus sounds is necessary to elicit soundscape orientation. Because the temporal structure of individual calls may degrade quickly as the sound of the chorus propagates through the habitat, orientation to breeding choruses based on acoustic information alone may be limited to relatively short distances in these two species.

多样的动物会借助环境声音在生态声景（ecological soundscape）中完成定位。然而，目前我们对声学信息的利用如何驱动定位相关行为决策的机制仍知之甚少。尽管蛙类合唱产生的声音会作为背景噪声，干扰集群内个体的信号接收，但这类声音同时也可作为具备信息价值的生态信号，帮助其他个体定位并找到正在进行繁殖活动的集群。本研究以北美绿树蛙（Hyla cinerea）和科普灰树蛙（H. chrysoscelis）为对象，探究了能引发个体朝向合唱声定位的声学线索。我们针对怀卵雌性个体，测试其对天然合唱声与不同声学信息类型的人工合成合唱声的趋声性（phonotaxis）行为。两种树蛙的雌性个体均会朝向天然合唱声，以及嵌入了单个鸣唱的实际时序与时域结构信息的人工合唱声移动。仅具备天然合唱声的时间平均频谱与调幅频谱，但缺失单个鸣唱的时序与时域结构信息的人工合唱声，则无法引发正向趋声行为。本研究结果表明，在合唱声的嘈杂背景中，来自单个鸣唱的时域信息是引发声景定位行为的必要条件。由于单个鸣唱的时域结构在合唱声通过生境传播的过程中可能快速衰减，仅依靠声学信息定位繁殖合唱群的能力，在这两个树蛙物种中可能仅局限于相对较近的距离范围内。