The 'silent' half: diversity, function and the critical knowledge gap on female frog vocalizations

Anuran vocalizations are crucial for species recognition and social interactions, particularly in reproduction. Historically, research has focused almost exclusively on male calls, leading to a male-biased perspective in anuran bioacoustics. Female calls have been often neglected due to their softness, making them difficult to detect. This review provides an overview of female calling behaviour in anurans, addressing a critical gap in frog bioacoustics and sexual selection. Specifically, we aim to (i) provide an overview of the current state of knowledge of female calling in frogs, (ii) propose a standardized classification for anuran call types, (iii) identify general patterns and challenges, (iv) recommend best practices, and (v) highlight areas for further exploration. Our literature review indicates that female calls have been documented in 112 species across 53 genera and 29 families, representing approximately 1.43% of all described anuran species. However, most descriptions are anecdotal or purely descriptive, with few functional analyses. Our findings underscore the widespread but largely overlooked presence of calling females in anurans. Expanding our research efforts on female vocalizations will improve our understanding of anuran communication. We hope this review motivates researchers to consider female frogs in future behavioural, ecological and evolutionary studies.