A comparative study of auditory sensitivity in the genus Bufo (amphibia)

Abstract

Multi-unit response from the torus semicircularis were recorded to obtain neural audiograms for five different species, subspecies and races of the genus Bufo: Bufo b. bufo, Bufo b. spinosus, two races of Bufo viridis, and Bufo americanus. All of the audiograms were clearly bimodal, with a low frequency peak and a high frequency peak. A less pronounced but distinguishable intermediate peak seems to be an indication of trimodality. In the low-frequency range, the audiograms of the five groups differed little or not at all. There were pronounced differences, however, in the high-frequency range. This frequency band includes the frequencies of the conspecific mating calls. The best matching between call frequency and auditory best frequency was found in the Bufo viridis group. While it is likely that factors other than the signal characteristics in the vocal repertoire may shape the sensitivity of the auditory system, it is notable that those anuran species in which the mating call clearly facilitates reproduction have a more pronounced sensitivity peak at the frequencies in their mating calls.