Ultrasonic frogs call at a higher pitch in noisier ambiance

• Published in: Current zoology 2015-12, Vol.61 (6), p.996-1003
• Main Authors: Zhang, Fang, Chen, Pan, Chen, Zhuqing, Zhao, Juan
• Format: Article
• Language: English
• Subjects: 低频噪声; 信号特征; 信号频率; 气氛; 环境噪声; 超声波; 青蛙; 音调
• ISSN: 1674-5507; 2396-9814
• DOI: 10.1093/czoolo/61.6.996

The ultrasonic communication in Concave-eared torrent flogs Odorrana tormota is believed to be an adaptation to avoid masking by the intense low-frequency noise of the rushing stream in their habitat. The acoustic adaptation hypothesis for ultrasonic origin predicts that some organisms subjecting to persistent acoustic interference from broadband, low-frequency en- vironmental noise, might shift their signal frequency upward into frequency bands with lower noise energy. In other words, low-frequency environmental noise might cause upward shifts of species＇ vocalization frequencies making their signals more conspicuous. Presently, it is unclear whether male O. tormota adjust their signal features in response to a change in the ambient noise level. We tested the prediction of the acoustic adaptation hypothesis by recording the vocalizations of male O. tormota in- habiting two streams with different background noise levels in Huangshan in central China and comparing their call features in- cluding the fundamental frequency （F0）. Results showed that the spectrotemporal characteristics of the vocal signals of males in the two habitats were indifferent, except the duration of the call harmonic segments and three parameters related to the call fun- damental frequency （F0）. In terms of the F0, the pooled and individual frog data showed that flogs inhabiting the noisier habitat tended to emit calls having higher F0. The higher F0 increases the signal-to-noise ratio, thus benefiting the detection of vocaliza- tion. Thus, similar to several anuran species, concave-eared torrent frogs also display noise-dependent adjustment of vocal pitch in their vocalizations for making them more audible