Males of many anuran and insect species call in large choruses. Chorusing intensifies competition among males for attracting mates, acquiring and defending resources needed by females, or both. The choruses are thus focal points for sexual selection.

However, choruses usually form in areas where the physical resources are required by females and offspring, and occur during seasonal and daily time periods that are favorable for courtship and reproduction. Chorus vocalizations are thus influenced by circadian rhythms and are typically concentrated in one or more periods in a twenty-fourhour cycle.

CAS Chengdu Institute of Biology Prof. CUI Jianguo's team pointed out the functions of vocalizations made by male anurans are to attract females or defend resources, and typically, males vocalize in choruses during one or more periods in a twenty-four-hour cycle, which varies, however, among species. Nevertheless, the causal factors influencing circadian variations of calling patterns in anuran species are not clear.

In this study, CIB researchers monitored male chorus vocalizations in the Emei music frog (Babina daunchina) for 17 consecutive days during the breeding season, while measuring its habitat air temperature and relative humidity in the course of experiments as well.  

Researchers also demonstrated that the circadian calling patterns were characterized by two periods of peak vocalization, which were observed from 0500 h to 0700 h and from 1300 h to 2000 h, while the lowest activity period was found from 2100 h to 2200 h. Both calls/h and notes/h were positively correlated with air temperature and negatively with relative humidity.

Overall, researchers' data indicate that the Emei music frogs (B. daunchina) could regulate their vocal activities based on the changes of physical micro-environment (e. g., temperature or humidity) to maximize reproductive success.

More results have been published in ASIAN HERPETOLOGICAL RESEARCH in 2011and this study was supported by National Natural Science Foundation of China and Chinese Academy of Sciences.

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