The Brazilian Torrent Frog Controls Its Paired Vocal Sacs Independently: Implications for Acoustic Parameters

Abstract

Communication often mediates social interactions, including reproduction, defense, and competition. In anurans, vocal sacs are used in communication during interactions, and they may be controlled in a variety of ways. Hylodes heyeri is diurnal and inhabits streams in the Atlantic Forest of South America. Its vocalizations are complex, probably due to living in a noisy environment, and can involve either unilateral or bilateral inflation of their paired vocal sacs. Here, we analyze the acoustic parameters of territorial calls when the Brazilian Torrent frog inflates one or two vocal sacs in response to territorial calls from playback. Males using two vocal sacs emitted fewer notes per call, had longer note duration, and higher frequencies than males using one vocal sac. We conclude that the strategy of control of the paired vocal sacs in this genus may be related to the energy expenditure for vocalization, mainly in close interactions between individuals.