Frogs have a unique trait - vocal sacs - which are specialized elastic chambers that help male frogs call. Despite frogs being well known for acoustic communication, Elias-Costa and Faivovich (2025) found that vocal sacs have been evolutionarily lost at least 146 times. This extreme number of vocal sac losses result in 18% of frogs lacking vocal sacs. They hypothesize that vocal sac loss may be due to a mixture of selection pressures related to avoiding the high energy demands of vocalization, avoiding predation pressures, and, in a few cases where species call underwater, not needing vocal sacs to help create airborne calls. In addition to highlighting vocal sac losses, the authors characterize the remarkable diversity in frog vocal sacs, including the extravagant bilobate or paired vocal sacs that have evolved multiple times in Anura. Their study provides a detailed and exciting roadmap for future vocal sac morphological studies.

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