Redescription of the Advertisement Call of Five Species of Thoropa (Anura, Cycloramphidae), Including Recordings of Rare and Endangered Species

Frogs of the genus Thoropa comprise six endemic Brazilian species on the Eastern side of the country. Little is known about their natural history, especially about their acoustic communication. Therefore, aiming to provide an overview of their vocalizations, we analyzed and redescribed male advertisement calls of three living and two possibly extinct species. The smaller species, T. petropolitana and T. lutzi, produce simple calls (one single note) with a higher frequency range than the remaining larger ones. On the other hand, the larger species present complex calls, with more than one note: T. megatympanum calls have three notes, T. taophora calls have four notes, and T. miliaris calls varies from three to six notes. Population snout-vent length negatively correlated with peak of dominant frequency as expected. However, highlighted differences between two populations of T. lutzi, which could indicate need of further taxonomic evaluation of those lineages. Peculiar morphology, such as the absence of vocal sacs and slits, may have contributed to their call variation and highly banded frequency structure. If the observed population differences reflect species-level differences, T. lutzi may be classified as a critically endangered species, as T. petropolitana. Furthermore, we provided a suggestion to an unusual behavior in frogs: calling with the mouth open in the smaller species of the genus.