Love Elliot K, Bee Mark A
Department of Ecology, Evolution, and Behavior, University of Minnesota - Twin Cities.
Anim Behav. 2010 Sep 1;80(3):509-515. doi: 10.1016/j.anbehav.2010.05.031.
One strategy for coping with the constraints on acoustic signal reception posed by ambient noise is to signal louder as noise levels increase. Termed the 'Lombard effect', this reflexive behaviour is widespread among birds and mammals and occurs with a diversity of signal types, leading to the hypothesis that voice amplitude regulation represents a general vertebrate mechanism for coping with environmental noise. Support for this evolutionary hypothesis, however, remains limited due to a lack of studies in taxa other than birds and mammals. Here, we report the results of an experimental test of the hypothesis that male grey treefrogs increase the amplitude of their advertisement calls in response to increasing levels of chorus-shaped noise. We recorded spontaneously produced calls in quiet and in the presence of noise broadcast at sound pressure levels ranging between 40 dB and 70 dB. While increasing noise levels induced predictable changes in call duration and rate, males did not regulate call amplitude. These results do not support the hypothesis that voice amplitude regulation is a generic vertebrate mechanism for coping with noise. We discuss the possibility that intense sexual selection and high levels of competition for mates in choruses place some frogs under strong selection to call consistently as loudly as possible.
应对环境噪声对声学信号接收造成的限制的一种策略是，随着噪声水平的增加而发出更大的信号。这种被称为“伦巴德效应”的反射行为在鸟类和哺乳动物中广泛存在，并且在多种信号类型中都会出现，这引发了一种假设，即声音振幅调节是脊椎动物应对环境噪声的一种普遍机制。然而，由于除鸟类和哺乳动物之外的其他类群缺乏相关研究，对这一进化假设的支持仍然有限。在此，我们报告了一项实验测试的结果，该假设认为雄性灰树蛙会随着合唱状噪声水平的增加而提高其求偶叫声的振幅。我们记录了在安静环境以及存在声压水平介于40分贝至70分贝之间的噪声环境下自发产生的叫声。虽然噪声水平的增加导致叫声时长和速率发生了可预测的变化，但雄性树蛙并未调节叫声振幅。这些结果并不支持声音振幅调节是脊椎动物应对噪声的一种普遍机制这一假设。我们讨论了这样一种可能性，即在蛙群中强烈的性选择和高水平的配偶竞争使得一些青蛙面临强大的选择压力，从而尽可能持续大声鸣叫。
