Department of Ecology, Evolution, and Behavior, University of Minnesota-Twin Cities, St Paul, MN 55108, USA.
J Exp Biol. 2010 Aug 15;213(Pt 16):2840-50. doi: 10.1242/jeb.044628.
Acoustic communication signals degrade as they propagate between signalers and receivers. While we generally understand the degrading effects of sound propagation on the structure of acoustic signals, we know considerably less about how receivers make behavioral decisions based on the perception of degraded signals in sonically and structurally complex habitats where communication occurs. In this study of acoustic mate recognition in Cope's gray treefrog, Hyla chrysoscelis (Cope 1880), we investigated how the temporal structure of male advertisement calls was compromised by propagation in a natural habitat and how females responded to stimuli mimicking various levels of temporal degradation. In a sound transmission experiment, we quantified changes in the pulsed structure of signals by broadcasting synthetic calls during active choruses from positions where we typically encountered signalers, and re-recording the signals from positions where we typically encountered potential receivers. Our main finding was that the silent gaps between pulses become increasingly 'filled in' by background noise and reverberations as a function of increasing propagation distance. We also conducted female phonotaxis experiments to determine the threshold modulation depth required to elicit recognition of the pulsatile structure of the call. Females were surprisingly tolerant of degraded temporal structure, and there was a tendency for greater permissiveness at lower playback levels. We discuss these results in terms of presumed mechanisms of call recognition in complex environments and the acoustic adaptation hypothesis.
声波信号在信号发送者和接收者之间传播时会逐渐衰减。虽然我们通常了解声音传播对声波信号结构的衰减影响，但对于接收者如何根据在声音和结构复杂的栖息地中感知到的退化信号做出行为决策，我们知之甚少。在这项关于 Cope 灰树蛙（Hyla chrysoscelis）的声学配偶识别研究中，我们调查了雄性广告叫声的时间结构在自然栖息地传播中是如何受到影响的，以及雌性对模拟各种时间退化程度的刺激的反应。在声音传输实验中，我们通过在通常遇到信号发送者的位置播放合成叫声，并从通常遇到潜在接收者的位置重新录制信号，来量化信号脉冲结构的变化。我们的主要发现是，随着传播距离的增加，脉冲之间的无声间隙会越来越多地被背景噪声和混响“填充”。我们还进行了雌性声向反应实验，以确定引发对叫声脉冲结构识别所需的调制深度阈值。令人惊讶的是，雌性对时间结构的退化具有很强的容忍性，而且在较低的回放水平下，这种容忍性有增强的趋势。我们根据复杂环境中假定的叫声识别机制和叫声适应假说讨论了这些结果。
