Acoustic parameters of Phyllodytes luteolus in conditions of low and high noise from vehicle traffic

Acoustic communication in animals can be affected by multiple biotic (intra and interspecific) and abiotic (e.g., wind and rain) natural noises. In addition, human beings produce additional novel sources of noise, which can reduce or inhibit the reception of acoustic signals by conspecifics, leading to behavioral changes. In this study, we investigated whether sound of conspecifics and road noise additively affect the acoustic parameters of the advertisement call of males of a Yellow Heart-tongued Frog (Phyllodytes luteolus). We hypothesized that males that vocalize in larger choruses (many males) and in areas close to highways (anthropic noise) will increase their temporal and spectral acoustic parameters, respectively, to avoid acoustic signal masking. We recorded the vocalizations of 38 males in environments close (N=18) to and distant (N=20) from highways in different social contexts (many or few individuals in the chorus). Contrary to our expectation, the results indicated that individuals exposed to road noise had lower dominant frequency calls than those from natural areas, and that the density of males in the chorus had no influence on the acoustic parameters. Furthermore, we found a positive relationship between body size and intensity, indicating that larger individuals can emit calls that can reach greater distances. The advertisement call of Phyllodytes luteolus has a high dominant frequency, with little overlap with the frequency of anthropic noises (roads), which may explain its presence and reproductive success of this species in bromeliads from urbanized areas.

动物的声学通讯易受多种生物源（种内与种间）与非生物源（如风、雨等）自然噪声的干扰。此外，人类活动会产生新型额外噪声，这类噪声可削弱甚至阻断同种个体对声学信号的接收，进而引发行为改变。本研究针对黄心舌蛙（Phyllodytes luteolus）雄性个体的宣告鸣叫声学参数，探究同种鸣声与道路噪声是否会产生叠加影响。我们提出假说：在鸣唱集群规模更大（雄性个体数量更多）以及靠近公路（人为噪声）的区域鸣叫的雄性，会分别调整其鸣声的时间与频谱声学参数，以规避声学信号掩蔽。我们在不同社会情境下（鸣唱集群个体数量多寡不一），分别于靠近（样本量N=18）与远离（样本量N=20）公路的环境中，录制了38只雄性个体的鸣唱声。研究结果与预期相悖：暴露于道路噪声环境中的个体，其鸣声主频较自然区域的个体更低；同时鸣唱集群的雄性密度对声学参数并无显著影响。此外，我们发现体型大小与鸣声强度呈正相关关系，即体型更大的个体能够发出传播距离更远的鸣叫声。黄心舌蛙的宣告鸣叫具有较高的主频，与道路这类人为噪声的频率重叠度极低，这或可解释该物种在城市化区域的附生凤梨生境中得以存续并获得繁殖成功的原因。