DISSERTATION RESEARCH: The neuroethology of ultrasonic communication in anuran amphibians.
Among the vocal vertebrates, anuran amphibians (frogs and toads) have long been considered the champions of acoustic simplicity. However, recent research suggests that this tenet of simplicity may not always hold true. Among the most striking examples is the recent discovery of a frog species, Odorrana tormota, that communicates ultrasonically (i.e., above the upper limit of human hearing), making it the first non-mammalian vertebrate shown to communicate with extraordinarily high-frequencies. Recent recordings of the vocalizations of another frog species, Huia cavitympanum, imply that anuran ultrasonic communication is not limited to O. tormota. A subset of H. cavitympanum's high-frequency calls are entirely ultrasonic, a feature previously undocumented in amphibians. Whether they use these ultrasonic calls to communicate, however, is not yet confirmed. The objectives of the proposed research are to 1) determine whether H. cavitympanum individuals communicate ultrasonically, using both behavioral and electrophysiological techniques; 2) characterize and compare the inner ear auditory organs of H. cavitympanum and O. tormota to determine the key specializations that allow these species to hear ultrasound. This research represents an opportunity to enhance our understanding of mechanisms used by lower vertebrates, with relatively simple acoustic behavior and auditory systems, to exploit an extraordinarily high-frequency communication channel. The discovery of previously undescribed mechanisms that permit high-frequency hearing within the distinctive anuran auditory system may provide insight into the evolutionary foundations of high-frequency hearing in all vertebrate forms, including humans. In addition, because the focal species of this project, H. cavitympanum, is found only on the island of Borneo, this research presents a unique opportunity to develop relationships with Southeast Asian researchers, and to present the results of this research to a variety of cultural and socioeconomic groups. This outreach provides a scientific and social bridge between disparate cultures that can contribute to future collaboration and student exchange.
