Altitudinal variations of acoustic organs in anurans: A case study from China

Abstract

Bioacoustic signals are considered to be essential to the social communication of anuran amphibians. However, some anuran species lack a vocal sac or tympanum, or both. We hypothesise that the variation of anuran acoustic organs correlates to altitude. We reviewed published literature concerning anuran species which inhabit China, and tested the general relationship between anuran acoustic organs and altitude. The result showed that both the vocal sac and the tympanum had a significantly negative trend to altitude, and that the vocal sac also significantly correlated to the tympanum. The interaction by phylogenetic relationships could be excluded. We suggested that anuran acoustic organs decline with increasing altitude. With increasing altitude, lower population density, low temperature, hypoxia and food shortage could be responsible for such degeneration. Nontympanic pathways of sound reception and ultrasonic signal system may be utilised to compensate for anuran acoustic organ degeneration.