Data from: Stressful city sounds: glucocorticoid responses to experimental traffic noise are environmentally dependent

A major challenge in urban ecology is to identify the environmental factors responsible for phenotypic differences between urban and rural individuals. However, the intercorrelation between the factors that characterise urban environments, combined with a lack of experimental manipulations of these factors in both urban and rural areas, hinder efforts to identify which aspects of urban environments are responsible for phenotypic differences. Among the factors modified by urbanisation, anthropogenic sound, particularly traffic noise, is especially detrimental to animals. The mechanisms by which anthropogenic sound affects animals are unclear, but one potential mechanism is through changes in glucocorticoid hormone levels. We exposed adult house wrens, Troglodytes aedon, to either traffic noise or pink noise. We found that urban wrens had higher initial (pre-restraint) corticosterone than rural wrens before treatment, and that traffic noise elevated initial corticosterone of rural, but not urban, wrens. By contrast, restraint stress-induced corticosterone was not affected by noise treatment. Our results indicate that traffic noise specifically contributes to determining the glucocorticoid phenotype, and suggest that glucocorticoids are a mechanism by which anthropogenic sound causes phenotypic differences between urban and rural animals.

城市生态学领域的核心挑战之一，在于甄别引发城乡个体表型差异的环境驱动因子。然而，表征城市环境的各类因子间存在复杂的相互关联，加之目前仍缺乏在城乡两地对这些因子开展实验操控的相关研究，这极大阻碍了学界明确究竟是城市环境的哪些维度导致了表型差异。在城市化改造的诸多环境因子中，人为声源（anthropogenic sound）——尤其是交通噪声（traffic noise）——对动物的负面影响尤为突出。目前学界尚未明确人为噪声影响动物的具体生理机制，但其中一种潜在路径是通过改变糖皮质激素（glucocorticoid）的水平实现。本研究将成年家鹪鹩（Troglodytes aedon）随机分为两组，分别暴露于交通噪声或粉红噪声（pink noise）环境中。实验结果显示，处理前城乡家鹪鹩的初始（束缚前）皮质酮（corticosterone）水平便存在差异：城市个体的初始皮质酮水平显著高于乡村个体；且交通噪声仅能提升乡村家鹪鹩的初始皮质酮水平，对城市个体无显著影响。与之相对，束缚应激诱导产生的皮质酮水平并未受到噪声处理的影响。本研究结果表明，交通噪声可特异性地塑造糖皮质激素表型，同时提示糖皮质激素可能是人为噪声引发城乡动物表型差异的潜在生理机制。