Auditory brainstem responses in the Chinese tiger frog Hoplobatrachus chinensis (Osbeck, 1765) (Anura: Dicroglossidae) reveal sexually dimorphic hearing sensitivity

Abstract Hearing sensitivity affects survival and reproduction in animals that communicate vocally. The Chinese tiger frog exhibits sexual dimorphism in body size, reflecting the evolution of mating behaviour and life-history strategies. In this study, we recorded auditory brainstem responses (ABRs) to determine hearing sensitivity in both female and male frogs. We also compared male and female hearing characteristics with the shape of the tympanic membrane in light of previous studies showing that smaller middle ear cavities improve hearing sensitivity. We found that ABR thresholds differ significantly between males and females, with the greatest sensitivities in both sexes at frequencies close to the dominant frequency of male calls. ABR thresholds were significantly lower in females compared to males for frequencies in the 0.9–1.3 kHz range and at 1.6 kHz. The tympanic membrane diameter was significantly smaller in females (5.94 ± 0.87 mm) than in males (6.71 ± 0.49 mm). Our results indicate that sexual selection has in all likelihood differentially affected male and female hearing sensitivity as well as the shape of the tympanic membrane in frogs.