1. State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
2. Department of Molecular & Integrative Physiology and Beckman Institute, University of Illinois, Urbana, Illinois 61801, USA
3. Department of Ecology & Evolutionary Biology,
4. Department of Physiological Science, University of California, Los Angeles, California 90095, USA
5. Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China

Correspondence to: Jun-Xian Shen¹ Correspondence and requests for materials should be addressed to J.-X.S. (Email: shenjx@sun5.ibp.ac.cn).

Sound communication plays a vital role in frog reproduction^{1, 2}, in which vocal advertisement is generally the domain of males. Females are typically silent, but in a few anuran species they can produce a feeble reciprocal call³ or rapping sounds⁴ during courtship. Males of concave-eared torrent frogs (Odorrana tormota) have demonstrated ultrasonic communication capacity⁵. Although females of O. tormota have an unusually well-developed vocal production system⁶, it is unclear whether or not they produce calls or are only passive partners in a communication system dominated by males. Here we show that before ovulation, gravid females of O. tormota emit calls that are distinct from males' advertisement calls, having higher fundamental frequencies and harmonics and shorter call duration. In the field and in a quiet, darkened indoor arena, these female calls evoke vocalizations and extraordinarily precise positive phonotaxis (a localization error of <1°), rivalling that of vertebrates with the highest localization acuity (barn owls^{7, 8}, dolphins, elephants and humans⁹). The localization accuracy of O. tormota is remarkable in light of their small head size (interaural distance of <1 cm), and suggests an additional selective advantage of high-frequency hearing beyond the ability to avoid masking by low-frequency background noise⁵.

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